A fun game!
I had a lot of fun with this game. The visuals are fairly good for a PlayStation 2 game, though some textures suffer under close scrutiny. There is a cool unlock feature as you progress through the story mode that unlocks fact sheets about characters and different mobile suits. The sound quality is also great - there's a feature where you can listen to music you've unlocked.
The part of this game I liked the most was the Co-op gameplay features. It's a lot of fun to jump in a mobile suit with a friend and blast some enemies out of the sky. The controls hearken back to the days of Virtual On in the arcades - simple to pick up and play, sometimes a little twitchy, but you can pull off some pretty great moves once you get used to the control scheme.
There's a huge selection of pilots, and just as good as a selection of suits to pick from. And if there isn't anyone you feel like playing as, you can always choose a random ZAFT or ORB pilot that hides behind their mysterious helmet! :)
My only complaint about this game is not about the game itself - it's my inability to speak or read more than a half-dozen words in Japanese. If you aren't fluent, be prepared to get a little frustrated - sometimes mission objectives are vague and unclear, leaving you failing a mission over and over until you figure out by trial and error exactly what you're supposed to do. Also, the AI can be brutal and cheap on occasion.
But, those two things aside, I highly recommend this game for anyone that's a fan of Gundam Seed!