One of the key advantages of the iPhone and iPod touch for developers is that they represent 'one platform' – in blessed contrast to the fragmentation of the Java market.

Yet it seems there are still differences within the iPhone / touch family. Touch Arcade reports that there are clear differences between the four devices – iPhone, 3G iPhone, iPod touch, and second-gen iPod touch.

Not least the fact that the new iPod touch has a 532MHz processor, compared to the 412MHz one inside the other three devices.

Meanwhile, Handheld Games Corp boss Thomas Fessler says the company discovered some issues with the differing performances during tests of its 3D TouchSports Tennis game.

"Where we can easily display two 1,500 polygon tennis players with 32 bones each on the iPod touch 2G and maintain fast and fluid game play, the original iPod touch just chokes, and in some instances so do the iPhones," he says.

It's certainly something for developers to be aware of before releasing their games.