I don't know how many people have seen this or not, so I wanted to mention it here. I'm a Palm OS user, and I carry a Treo 700p. That said, I try to keep up on what is going on over on the Windows Mobile side of the Palm house.
While researching the Treo 750 Updater 2.25 (the one that adds Windows Mobile 6.0) for a customer over on the Palm Community Help Forums, where I'm a moderator, I ran across the directions for using the Updater 2.25 Recover Tool.
I'm actually excited to see that Palm has packaged this tool into the upgrade kit. While I don't have a Windows Mobile device to test this on, the tool appears to give customers a second chance to recover from a Treo that was "bricked" by a failed upgrade.
AT&T and Cingular Wireless customers can download the 2.25 Updater here. The directions for using the recovery tool can be found here.