We've been pining for an over-the-air ability to update Windows Mobile firmware for quite some time now. From the introduction of Windows Update in WM6, which has never been used, to the promises of Windows Mobile 7, this feature has been on the cusp of being a reality for far too long.
Interestingly on the HTC Sprint Snap if you look under Settings --> Device Management, you can see a Firmware Update option that seems to actually be functioning. When launched there is "FUMO" in the title bar which stands for Firmware Update Managed Object as documented in the MSDN Center for Windows Mobile. Furthermore, it is checking in with a server, responding with "No firmware update is available" after a few seconds.
We know devices like the AT&T Epix can do these types of updates, but we haven't seen this feature from HTC,WM or Sprint yet (as far as we remember).
Now the big question is will Sprint/HTC actually use this anytime in the future, perhaps for WM6.5 or just bug fixes? We bet on the latter due to the how the OTA system works. Lets hope we can give it a go sometime.