Definitely not as good as any of the Saturn or Arcade installments. Left me with a bad aftertaste.
For starters, it's mission based instead of a fighting game. It's as if you saw Virtual On and assumed you'd be playing robot-a-robot but instead are playing ONLY the Devil Within minigame from Tekken 5. Imagine the learning curve of mech controls, dumbed-down, with the beat 'em up style of roaming about firing at small MTs. Only this isn't Gungriffon Blaze or Armored Core so it just doesn't work. Once you beat a tiny 40 second mission, you're treated to a pessimistic voice over. "But that didn't stop the real tragedy" or something like it after every success. Then another 20 second load for a 50 second "boss battle," then "Life is fleeting. We all could die this very minute because of terrorism!" is yelled at you for whatever reason, and repeat until you turn off your PS2.
Well, there are lots of robots to unlock and use in vs mode, where it should redeem itself, but... you won't be using the vs mode very often. You see, it's harder to play this game the way it was meant to be played because the controls had to be dumbed down to mission based 1p standards and therefore you're just staring at the floor, flailing and groaning, during multiplayer bouts instead of having heated mech battles with worthy adversaries. I had a friend, also into Virtual On, come over and challenge me. We spent a few rounds trying to face eachother, period.
The best parts of this game are that the graphics aren't bad and the depressing voice over is unintentionally hilarious at times. The worst parts are everything else. All things considered, it's a boring mission-based mech game with a crappy story and cracked-out controls but there are far worse games, some of them coming out today. If you feel you can overlook the badness, why not give it a try if you've really got that much time on your hands. I personally would recommend you find the Saturn version, though.