If you're into that type of game, yes, I believe it is. Kil.a.ton is the best of its kind, and I enjoyed it more than iShoot. But don't rush into purchasing. Play the lite version for a few more days, and, if you still like it, then consider buying the full version.
I'd say its worth it. If you like this, then try out Star Hogs. Best turn-based artillery game on the iPhone.
I bought it, if that makes a difference to anyone. Best scorched earth like game I've played on my iPod. I love the simultaneous fire mechanisms. Just wish there were more players online.