I remember having updated it to Windows mobile 6.5 (German version) back in 2009, that process was very easy.
One prominent handset vendor told us Windows Mobile 6.5 upgrades aren't cut-and-dry because the carriers are afraid unforeseen issues involving running the new OS will break their fragile networks.
Upgrading a phone's OS could create behaviors that weren't there the first time the carrier approved the device.
Essentially, the carriers are treating each Windows Mobile 6.5 upgrade as an entirely new phone that needs to be approved all over again.
(Anyone with an unlocked GSM device that works with any SIM card knows this is a dubious claim.) A Verizon spokesperson pointed out that not every device running Windows Mobile could be updated anyway; that capability needs to be built into the device from the beginning.
Samsung Jack SGH-i637 (AT&T) Samsung's shrewdly updated Black Jack (now simply the "Jack") builds on its predecessors' positive attributes.