i own steel battalion and it is awesome. i dropped $150 for a used one at eb a few years ago, and while that was alot of money, as a video game collector, i just had to have it. i never picked up the online only, line of contact version though, becuase by the time i found that, i had already cancelled my xbox live account (i'm not one for online gaming).
it was a very immersive experience to play this game. I haven't played it in a while, now that i am married and have kids, i just don't have the time to play games like i used to when i was single. but i remember spending hours in my old apartment playing this game. nothing quite compares to steel battalion on a 102" screen. it is an experience.
if you ever see it for a reasonable price, get it..it is worth owning. even for thing else, just being able to say you have one. I have not seen anyone who has seen the controller and not been amazed.