I use Exchange 2010 RC and it works fine apart from:

1. if phone looses connection to net - I need to do a manual sync to get it going again. Which means I cant trust the Sync function to work.

2. It syncs all folders :-( so I'm limited to last 1 month since taking all way back gets now 9GB exchange data) - please lets get folder selection.

3. I cant move mails to another folder from N900. (Or have not found the function)

and last but not least..

going into mail is so slow. When you navigate from mail accounts overview to a mail account - it can take 10-20 seconds before you see folder overview. From folder overview to inbox can take another 10-20 seconds. But that is not MfE specific.

and MfE is very CPU hungry. I think MfE is the /as-daemon process. Syncing mail pushes /as-daemon to 97% CPU usage for 30-60 secs - which is a bit excessive compared to Roadsync on the S60 platform that takes less than 10% for 3-4 secs to do an updated sync.