You really have nothing to lose by downloading Eliminate Pro. Its siren song will call loudest to hardcore gamers, but anyone can and should give it a shot. That first, free allotment of power cells will fuel your habit for about an hour, which is enough time for you to decide how you'd like to proceed. Some players might feel nickel and dimed by the in-app purchases, though the experience almost seems to recall the old coin-operated arcade games of yesteryear.
Casual players can dabble for free, while hardcore addicts can pay as they go. Any way you slice it, this is one of the most polished full experiences you'll find for free on the App Store.