Sprint's just churning out Windows Mobile 6.1 as fast as they can it seems.  Yesterday we saw a new Mogul ROM surface, and today the Touch gets the same update.  Users are reporting a quicker GPS fix and overall improved stability over previous custom ROMs.  Since this is an official Sprint ROM there is no need to unlock your device or worry about bricking it, but it also means it will only work on Sprint devices.  Head over to XDA, download the .exe, connect your device and run it!

HTC Touch CDMA Specifications | Review

source: XDA Developers