I haven't tried it yet, but a beta copy of this new version has just been made available from Microsoft.
See:
http://www.microsoft.com/windowsmobi...ivesync42.mspx
It seems that it supports devices from Pocket PC 2002 through to the latest Windows Mobile 5.0 devices, and includes a number of fixes as well as a USB Troubleshooter for sorting out issues when connecting your device to your PC. Fixes include better support for Norton Anti-virus software and how proxy servers are handled when accessing the Internet via the PC.
Of course, if AS 4.1 is working for you, there is a good case of "if it aint broke, don't fix it"!
Cheers, Chris