MobilityToday’s David Ciccone claims that the HTC Diamond does not support the 850MhZ band used by most American GSM carriers. While this doesn’t make roaming entirely impossible, it definitely means that users must expect worse coverage while traveling.
User discussion on the topic is still active at the moment, with several people claiming that the Diamond will ship in two different versions(USA and Europe); with each one lacking one band that the other supports.
Anyways, Expansys is currently taking preorders for the device and confirms the information above - looks like the (european version of the) HTC Diamond does NOT support 850MhZ…