Folks at Precommunity got some hands-on time with the Pre, and suprisingly, the device they previewed was a GSM version of the new handset. The device was handled at the Mobile World Congress in Barcelona, although Palm has not made an official announcement for a HSDPA/GSM version of the device. In photos and a YouTube video of the device, the back cover is removed, revealing a Vodafone SIM card under the battery.
Palm has since commented on the European UMTS version of the Pre (in contrast, Sprint runs an EVDO version), and apparently the European version multitasks better than Sprint's. Pam Deziel, Palm vice president of software product management describes how the European version can surf the Web while making a phone call at the same time, while the EVDO version is incapable of doing both simultaneously, because it has to pause the Internet connection temporarily while it makes phone calls. A carrier has not yet been announced for the UMTS version.
As for bringing enhanced functionality back home? JGadgets says technically yes, it's possible to purchase a UMTS phone from a foreign land and bring it back to the US. This would probably be the only way, as agreements with providers will prohibit an unlocked version to be sold in the US.