1. The story is crap - and honestly PSO's storyline is better then PSU's and it's ME saying this, IE the person who has gone beyond apeshit on how much I hated PSO's storyline.
I would disagree in that PSU's storyline is much more coherent and far more developed than PSO's ever was. It's easy enough to follow, rather than having to hunt for it, and it doesn't have any uber-stupid contradictions such as the whole "Dr. Montegue, a Numan, created the Numan race".
However, on the downside - PSU feels less like an epic mix of Star Wars and H.P. Lovecraft like the previous games were, and more like a sci-fi Naruto. If you like 4-Kids storylines, you'll love PSU's storyline. The entire affair is trite and cliche, and you're only getting 1/4th of the storyline (Ep II and further expansions will build more on it in a very .//hack-ish style) so it feels very incomplete.
Time will tell on this one.
2. The characters are rejects from PSO's storyline
Some are, many aren't. By and large, many of the important characters are twisted corruptions of their classic PS counterparts... such as Izuma Rutsu who (thus far) has shown himself to be rather weak of character, cowing over to the Divine Maiden and irrationally uncoorperative. Lutz wouldn't help Alis until he recieved a letter from the Governor informing him of the danger that Algol faced. He could care less about her quest for revenge or the toppling of a temporary despot. Rutsu, on the other hand, faces the very clear destruction of all civilization in Gurhal - and instead chooses to protect his precious Divine Maiden.
3. The voice acting is bad enough to make you crindge
Some is, and some is quite good. Karen, Ethan, Tonnio, and especially Hal are horribly bad. Most of them, like Dr. Tomrain, Leo, Lou, Maya, etc, are average. And some of them REALLY shine, such as Hiru Vol, Magashi, and Kou Taragi.
If you've ever played Star Ocean: Till the End of Time, know that PSU's voice acting is far, far better. So you don't really have much to fear from bad voice acting. And honestly, most of the problem is the directing rather than the voice actors. If you play through a chapter a second time, you'll get an alternate episode preview which is just voice - no graphics. The VA's have much more room to be fun and fullfill their roles without worrying about pacing in synching up the lip movements. They're actually quite good and humorous.
4. Playing the game is vastly to easy and enemies drop insanely quickly and you level like you've got cheats on.
This is true. At no point in the game should you die, even as a totally inept gamer, except on the odd occurance of 1-hit kill Megid or being frozen just before being slammed by like 8 or 9 high level Bartas.
5. Playing through chapter 4 in order to unlock the extra mode (offline freeplay basically creating a character and exploring the PSU worlds) is a chore in itself but the free play itself is shallow and you are FORCED to use the crappy AI characters from the main game if you want to party up.
I never felt forced to reach chapter 4 (chapter 5, technically, since you don't get it until Chapter 4 is done) in order to unlock extra mode. There's nothing in Extra mode, really. It's like playing PSO v.1 online on a completely empty server, and no quests, no NPCs, no storyline, nothing.
6. The ally AI is HORRIBLE, your allies will do absolutely crapshit to help you, honestly your better off soloing.
Yes, the AI is below even below average. I wouldn't even say they're better than PSO's NPC's. In PSO your NPCs would attack regularly, but with only a single strike. In PSU, your NPC's can do combos, heal you, use attack PA's, etc... the problem being that they spend 5 minutes circling the monster and eating damage before they do anything. They're also highly likely to just run in circles, stop moving, or get lost. They still make good distractions and hate pullers though. In a way, it's good that they're so bad, because if they were competent you wouldn't even need to play the game. It's so easy, you could just walk forward and let them slaughter everything.