Pros:
Optimus Prime continues the be teh awsum.
Jetfire was a well-rounded and plausible curmudgeon.
Wheelie was the least annoying he's ever been.
Soundwave was Soundwave (though the vocoded voice was such a careless omission.)
6 original Primes, plus The Fallen. Oooh!
Ravage was Ravage. And his 2-D blade Transformer thing was pretty cool.
Starscream was appropriately fawning and obsequious.
Pretenders! (though...Alice? Do we want a Transformer called Alice?)
John Turturro was good. Actually something going on there.
Megatron was a freaking flying tank!!
The Fallen was Tony freakin' Todd!!!
Cons:
The Constructicons were two places at once (unless they were clones or something...whatevs).
Devastator was taken down a bit easily, as was the Fallen. Deus ex machina, again.
Jolt had no dialogue.
Springer? Wasn't he supposed to be, y'know, in the film?
Skids and Mudflap, while amusing, were racist stereotypes. Jar Jar Binks anyone?
The Autobots didn't have much to do really, dialogue or otherwise. It'd be nice to have some character development. In two live-action movies, there's been less character development than in one animated one.
SofaMan - Occasionally Battling Evil with his Mighty Powers of Indolence