Eliminate [App Store] has been somewhat of a sensation on our forums since its initial release in Canada. Our Canadian members (as well as quite a few "Canadians") have really enjoyed having early access to the game, and aside from the somewhat expected reactions towards the energy system and in-game microtransactions, it seems like everyone is having a lot of fun.
We extensively previewed Eliminate last month, and very little has changed since then short of some tweaking of the energy system and increasing the recharge time. Still, as mentioned in the preview, you can play Eliminate for as long as you'd like to without paying a penny-- Your character advancement will just be slowed as you will only earn credits (the in-game currency used to level up and buy equipment) while you're energized.
I highly recommend downloading Eliminate. It's free, you've got nothing to lose. Regardless of how you feel about the payment system ngmoco is using to fund the game, it's still one of the more impressive multiplayer games available on the platform, and experiencing that won't cost you anything.
Update: Eliminate is available in most major iTunes markets, it seems there are still some countries that haven't seen it yet, but most European stores as well as the US store are currently stocked with Eliminate.
App Store Link: Eliminate, Free