Not surprisingly some geeks were able to extract the .NET Compact Framework 3.7 version which was contained in one of the latest Windows Mobile 6.5 ROMs. The .NET Compact Framework 3.7 is now available on some sites for download as CAB file. Unfortunately the extracted run-time environment is without a change log which let’s us developers in the dark what really was improved.
Rumors are going around that the .NET Compact Framework 3.7 seems to be faster in speed with large applications. But there seem to be compatibility issues with the official .NET Compact Framework 3.5 release.
More information can be found under:
http://forum.ppcgeeks.com/showthread.php?t=71466
http://forum.xda-developers.com/showthread.php?t=525138
But I recommend to wait a bit longer until the official release is available!