Guys over RedmondPie has just got some exclusive screenshots of unlocked iPhone 4 on baseband 02.10.04 running T-Mobile network.
This iPhone 4 is unlocked by Gevey SIM which was announced few days ago.
Gevey SIM for iPhone 4 basically works by forcing the activation of the baseband using the emergency dialer, and it is also said to be vulnerable up to iOS 4.3.
We totally advice and recommend you wait for a legal iPhone 4 unlock from the iPhone Dev Team which will be possible soon thanks to the 40-bit NCK exploit for iPhone 4.
Here's a video in action: