Looks like crap, apparently. Okay, we'll admit that FaceTime is cooler than we thought, but having it only work on Wi-Fi makes it less useful. But after seeing FaceTime fail over 3G, we'll take less useless over being unusable.
The guys at LaptopMag tested out a FaceTime call over 3G by using the HTC Evo's Mobile Hotspot feature, with its 4G turned off. The Evo used its 3G network to broadcast a Wi-Fi signal to get the iPhone 4 to connect to. Sneaky. The other iPhone 4 was connected to a real Wi-Fi network and if things went swimmingly, it'd be another instance of AT&T handcuffing the iPhone. But swim it did not, their video test went horribly wrong. According to them, "audio came through only in patches, and video was like a slideshow at best".
Of course, the entire setup, from res to bitrates, is optimized for WiFi, so this isn't quite a fair test. But it is an interesting setup in terms of seeing how Facetime does under the pressure of a bad internet connection. What happens when your wifi is very slow, or you have a really slow DSL connection? Same as if you had a 3G connection isn't it? It either scales down or it gets lousy. [LaptopMag]