MetalStorm: Online is a free--and impressively executed--multiplayer flight sim, but with a potentially frustrating in-game economy and erratically balanced matchmaking.
The interface and basic gameplay of MetalStorm are a joy: with smart use of your accelerometer and a few thumb controls on your "HUD" (arrows for brake and afterburner, buttons for guns and missiles), MetalStorm immerses you effectively in a jet cockpit for a tense dogfight experience, with cinematic music and great-looking terrain to complete the effect. You fly a modern jet equipped with an upgradeable cannon and missiles, and you can duke it out with increasing numbers of AI jets in Survival Mode (solo or with a friend), or you can play 2.5-minute matches in Versus mode, either with a GameCenter friend or a random online matchup. These matchups take into account skill level and time played, but it's not clear how or whether jet upgrades are factored in--and that raises issues about the game's "freemium" economy. As with similar free games, you have to pay in-game currency to upgrade your abilities (in this case, to increase your plane's agility, armor, damage, and the like), and you can either slowly grind out the money you earn, winning credits for playing and leveling up, or you can pay real money to accomplish this much, much faster. To add to the pain, many of the upgrades are disposable items (missiles and ammo), so progress can feel three steps forward two steps back.
Because the core game is so fun and well done, these balance issues are all the more annoying, especially with the online matchmaking. (And of course MetalStorm has the inevitable come-ons for a freemium app, in the form of ads--which can crash the app--and relentless sales and partner promotions.) That said, MetalStorm can be a lot of fun, even for free, but plan to pay up (or log a ridiculous amount of flight time) if you want to play competitively.