Over 50 stages, multiple routes, faster auto battles, and a superb cast make this one of the best SRW's to date!
The game's cast is wonderful, from Gundam favourites such as Wing, Seed, Victory, to Go Nagai's robots; mazinger z and getter robo, even including new comers from Gurrenn Lagann.
Gameplay wise, it's a strategy game where you control a group of robots, and your goal in each stage is to eliminate all opponents on the map. There are exceptions though where you have to drop a zero robot/character to a specific location in the map to finish the mission, although those requirements are rare; unlike previous SRW's, those requirements were a plenty.
I would say that if this is your first SRW, or if you've been in hiatus and this is the latest one you've played, Z2 is somewhat 'noob friendly' to players.
Overall, it's a great game, and if by any chance you can get part 2 (Sesai Hen) when it comes out, go ahead!