Ngmoco's Eliminate has been building up buzz ever since it was announced, and now the first-person shooter is out on the App Store to try for yourself. As you can see above, it offers some relatively basic FPS gameplay when compared to shooters on other platforms (I've been having a lot of fun with Borderlands lately), but given that this is the iPhone we're talking about, this kind of twitch 3D gameplay is actually pretty impressive. You can play online over 3G or Wi-Fi, and as you play, you can earn credits and level up, which gives you access to more weapons and better gear. The game itself is free, but it's all based around a microtransaction system where you buy "energy" which allows you to earn those aforementioned resources. You get a certain amount of energy per day on your own, and if you use it up, you can't progress any further unless you get out the wallet or wait another day. And the game uses ngmoco's own Plus+ social interface to track leaderboards and accounts. Interesting plan, and we'll have to see if players vibe with it or not. Some have already voiced strong concerns about the in-game pay-to-play microtransaction system.

If that doesn't vibe with you, and you'd rather play some old-school (and old business model) FPS gameplay instead, id's Doom Classic also got released on the App Store last weekend. That game comes at a cost of $6.99, but then again, with old-school Doom, you know exactly what you're getting into. And you won't have to buy any extra energy to charge your BFG and slay any demons you happen to come across.

It was just yesterday that Apple announced they would allow free apps to enable in-app purchases, and developers are already jumping on the "get the app for free, buy the content later" business model as quickly as they can. ngmoco came out swinging, as Touch Arcade reports, with both a free intro version of Rolando 2 out for purchase, with later chapters of the game as add-ons. They've also been working on a shooter called Eliminate, and we're now told that title will be free as well, with extra content to buy later.

The creators of Urban Rivals, an app that is based on a virtual trading card game, have let us know that they too plan to go the free-with-microtransactions model as soon as their app is released, and though we haven't actually heard from Tapulous, Andrew Lacy told us outright that the only reason Tap Tap Revenge 3 had a 99 cent price tag on it was because of Apple's limitation, so we'll expect that app to go free as soon as it can.

Clearly, there's a drive for this model on the developer side, but the question will be just how much this echoes with consumers -- certainly the "download a trial, buy more later" model has worked well on other platforms, so we can expect it to work here on the App Store as well. But on the other hand, just as when the App Store first opened for business, it's a very "wild west" moment -- everybody and their brother is offering up in-app transactions, and they're all of varying prices and quality.

My guess is that we'll see a few "hits" -- a few free apps that everybody buys content for (Tap Tap Revenge 3 is a good guess; considering that because you know most of those songs, there's much less guessing on what the quality of the transactions will give you). At the same time, there will likely be apps that everyone agrees aren't worth the in-app purchase (it's the old story of "horse armor" when Xbox Live started doing microtransactions). Until we find a good balance, where quality meets price, odds are that it'll be tough for consumers to know just what's worth it, and thus tough for developers to convince them that their content is.