Hmm...Personally, I thought it was an excellent game. 'Course, I'm probably biased about it, but everyone is in some small way.
I both agree and disagree with many things said on this thread. I suppose I should put up a list of pros and cons of my own...
+The Deck customization is pretty awesome. Sure, a number of powerful commands are button mashable (Time Splicer is an excellent example), but there are others that are not, and some commands don't even use button input, you actually have to use the analog stick (Terra's final Finisher, Ventus' Multivortex, etc...). There's a decent amount of variety in the Command system, and I tend to enjoy making my own epic decks. It's certainly a step above CoM's Card system, though that had it's own perks.
+I know I didn't read every post, but did anyone mention the Shotlocks? I found them an innovative addition to the KH series. It's a pretty useful way of getting rid of crowds, and they are well varied, as it's not all button mashing. True, I tend to forget about them during gameplay, but the same could be said for the D-Links...
+While most bosses are easy, the Three Hardest Bosses (Iron Imprisoner IV, Vanitas Remnant, and the Mysterious Figure) do require some strategy to take them down. VR has multiple resistances and forces you to use potions and other "Items" to heal (Really, who's needed to use any items to get through the game? Cure spells are easier) to keep the boss from healing himself, and MF has multiple attacks, and little way to predict how they'll go, so you really have to use your brain to take him down. It adds to the strategy aspect.
+The Music is awesome as always. I could listen to it over and over and over and...you get the idea.
+-The D-Links. Like with summons, I have mixed feelings about them. Indeed, many are cool and fairly useful, but I've never really needed to use them apart from Journal completion.
+-Command Board. Innovative, and a good way to level up commands, but it can get tedious, and the fact that opponents will "steal" your commands (Keeping them from getting CP unless you can snag 'em back) makes it annoying on occasions...I really only use it in the Mirage Arena, since you can choose to only go up against one CPU instead of dealing with another potential migraine. It can be fun, and I have won more games than I have lost. It's fairly easy for me.
+-The Mirage Arena in general. Very Mixed. It's fun smacking around hordes of Unversed and rebattling past bosses, but I would've liked there to be an option solely for rechallenging previous bosses. Some of them are very fun to Fight (For me, Braig and Lucifer come to mind, along with the Spirit of the Mirror), and it would up the replayability a smidge. I know, there are those pesky tech limitations, but it would've been nice. Also, I love Rumble Racing, it's fun just to cruise around on the Keyblade Ride and it's a different way to pass the time. I haven't tried Versus yet (Don't have anyone around me with the game...), but I'm sure challenging actual opponents will be more fun than facing CPUs all the time. That's what keeps the SSB series so fun at it's heart, right? And of course...No pausing. I understand why there would be no pausing in Online mode, but having no way to pause except put the PSP in sleep mode is VERY annoying when Offline. Could've been better, but it's fun.
+-The storyline. I'm just gonna lay it all out in one piece, since there is good and bad. People complain about the speed of the worlds and thus the storyline, but the game is divided between three characters. There is a reason, and if you look at all three stories of each world in "the big picture", or however you wanna say it, it does make perfect sense. Also, on the subject of Disney, let's face it. KH began as Disney and Square Enix (Or Squaresoft, as it was back in the day), and it's not gonna change anytime soon. Useless Filler? Maybe, but I like how they kept to the original stories while being able to add their characters in (Especially Deep Space. They did that world very well). Also, Disney Town wasn't as boring as everyone makes it out to be. Sure, there wasn't much story for each character, but as a whole it was fairly good. It explains Pete, and provides a decent diversion from the main gameplay. At heart, it's a minigame world, so Story isn't the first thing to come to mind. Please, stop complaining. On the subject of FF cameos, I guess it's a case of WYSIWYG. Olympus has always been the main place for FF cameos, and they didn't do so bad with Zack. Sure, the Hollow Bastion gang would've been nice, but when you really think about it, it might've just gotten confusing. I would've liked to see a secret boss battle with Genesis. That probably would've been the most FF story they could give without too much hassle. I've even got potential scenarios in my mind (and on one of the various threads around here)! On the Characters themselves, not too bad. Terra constantly struggles to deal with the Darkness within, and that made for an excellent story (Even the Disney Town bit relates to it). Ventus searches for Terra in the beginning, but after RG, it turns towards him wanting to make friends, which really gives you the Sora connection, another plus. Aqua....I will admit, she could've used better storyline. Mostly she's just following the boys, finishing off what they started. For her, RG, Deep Space (where she gets there second), OC, and KG are the highlights but she needs more. I assume that since she'll make an appearance in future KH titles (3D, perhaps?), she'll get better story. As far as her role in BBS, very mixed. On the subject of the Princesses, Enchanted Dominion's story ties closest to the main story, and is in fact the best of the three (Of course, we know by now that Maleficent always has her hands in the Worlds' dark affairs...). No qualms there. Dwarf Woodlands could be a little better, but it does follow the storyline well. Ventus' parts are perhaps the highlight of it. Terra's role as the "Woodsman" works well too. For Castle of Dreams, Ventus is the comical highlight (and I quote..."Someone tell me how I got so SMALL!"), and Terra's isn't too bad. I liked how event music was used in an event battle. Certainly gives off the emotion of the moment. In Aqua's, I was disappointed. Tremaine and the evil stepsisters just get destroyed by the Unversed they summon. Sucky, for certain, but it does un-canonize those annoying movie sequels *Insert evil chuckle here*. Probably the worst of the three, but overall they explain the first three PoH in KH1, and do have an impact on the characters themselves (Evidenced by Aqua's ending in the Final Episode). Pretty good, in my opinion.
For the Keyblade Graveyard, I have to say it ties the story together very well. The final fights against Terranort and Vanitas w/ X-Blade (both Ventus and Aqua) are epic, and it does, in the end, explain everything KH1 onward. The Final Episode is short, but well done. I truly felt the emotion in the final cutscenes, and it just makes Blank Points all the more important...
That's pretty much my take on story.
+-The Voice Actors. No need to stress your eyes, it's not nearly as long as the previous section. I have no qualms about the Voice actors, all of them did fairly well...Except Snow White. No qualms about dialog, it's just the voice didn't sound...right, to me...Not the best in the bunch...but overall, very well done.
+-Ice Cream Beat. Most people would call it Ice Cream Hell, and I have done so a number of times on Facebook. Nonetheless, I've managed to get the hang of it, and it's not so bad. You've really gotta learn patience with it, not wanting to have that button mash impulse prevent you from getting a high score. Overall, mostly negative, but I do love Gummi Ship -Blast Away II-'s Master mode. Just my kind of rhythm. Most hated? Destiny Islands. Patience is a virtue, but they like throwing feints at you ("Hey, the blue duck's still moving, I guess it'll be easy! Wait...The rings are showing around Red and Green! Crud, the Blue duck distracted me..." How many of us have thought this? Be honest.) and switching between ducks like the wind. Also, I get the feeling that there is a difference between each character's version of the song...I could be wrong, but still. Overall, it's a meh. Somewhat fun, often annoying. Best saved for last...
-Terra's lack of useful commands. Ventus has the best evasion abilities, and Aqua's magic variety is superb. But Terra is left in the dust with his unchainable, split second Slide and very few moves effective against the Secret Bosses. I have to say the Sonic Blade is his best command, but considering the Dark commands he has, I expected more out of them in terms of versatility (Apart from Dark Volley. The Shotlock is always useful), perhaps a few with high invincibility frames. I hope Eraqus Sentiment is made so that Terra can pwn him, but is harder for the other two. Vanitas Remnant is Ventus bait with Tornado, and Aqua's Barrier puts MF in the same position (Not to mention Ventus Dodge Roll is the ultimate evasion maneuver in this game). I expected more from him in terms of gameplay, it feels like SE didn't give him much love in that department...
+-The Command Styles. Love the variety and usefulness of some, but I hate how you can't turn them on or off. How many times has shifting into a command style you don't want killed you during a battle with I.I. IV? And Sky Climber, while fun, negates Ventus epic Dodge Roll. I thank one of the people on this forum for telling me about the use of Milky Way, it saved my skin during the MF boss fight. I realize they require certain commands to activate, but for their first one, pretty much every attack/magic command (depending on character) they have can activate it. It would be nice to turn the potential off without sacrificing useful commands, should they implement this in future titles.
...Overall, not much bad to say. I gave it an amazing, but that's because I'm still having fun playing it. Definitely a good entry to the series, but nothing is perfect. Don't expect it to be.
...If there are any spoilers I need to cover up, please let me know. At this point in time, I'm not sure what's still spoiler and what isn't aside from Keyblade Graveyard and Final Episode. So if I did spoil someone, I apologize.