Apparently some of the latest Windows Mobile 6.5 ROM’s contained a new version of the .net Compact Framework, version 3.7. This software has been duly liberated for use with other Windows Mobile devices by the usual suspects.
Unfortunately the run-time environment came without a change log, so we don’t really know what improvements if any it brings, but ever optimistic users gave reported faster speed with applications which use the code heavily. On the other hand some others have complained of incompatibility between .net 3.7 as leaked, and the official .net 3.5, so use at your own caution.
WMPoweruser.com Blog Archive .Net CF 3.7 leaked, may feature performance improvements