The good old Ridge Racer from Namco :)
Graphics - Almost as good as the PSP version. Very solid graphics, one of the best on iPhone/iPod Touch platform. It's of cause better to run this game with the latest iPhone 4 or iPod Touch 4 to avoid any performance issues.
Audio - Ridge Racer series always has good musical scores, this one is no difference. However, the cars' sound can be improved further.
Gameplay - The game has reduced the difficulty to counter control problems, for example, you get way less penalty for hitting the wall or cars than those on other platforms. However, due to the nature of platform, the motion control is not that easy to use, you better change to on-screen controls instead. An other issue: all those unlocking stuff. Apart from those need to purchase to unlock, you don't have many choices when you first run the game. To unlock maps and cars, you have to be 1st on every map which can be hard for some people (mostly just controlling issues). This is an arcade racer so no career mode included, just like the PSP version. You can play with these modes: Arcade, Duel (local wifi), Survival, Time Attack. One more little issue: you can't change screen orientation.
Summary - Almost a perfect racer, but missing some points due to unlocking stuff and controlling issues (even with the on-screen controls). If you're fans to the series, then why are you still reading this, log in and buy it. Or if you're a new comer who have played conventional racing games (simulation games like GT, Fonza or NFS), you might find this game quite easy to play. In all, this is a gamer's game (or Hardcore Gamer), not suitable for light users who play games for relaxation.