With the release of Leopard, I have a little work to do to get MsgFiler fully compatible. I’ve already posted revised installation instructions on the MsgFiler webpage. Users who are using the app on Leopard have probably noticed that mailboxes are showing up twice. This will be fixed in the next version, which I hope to get done before the New Year. Leopard users will also want to bind a new command-key equivalent for MsgFiler by going to System Preferences / Keyboard and Mouse / Keyboard Shortcuts.
The delay in getting this out is due to the fact that I’m rewriting the entire app in Cocoa and Objective-C. It’s probably a trivial task for someone who’s proficient in Cocoa. For me, a relative newbie to Cocoa development, it’s taking longer than I expected.
tow.com 
Congratulations on the update. MsgFiler now works super FAST even across IMAP and I can work in Mail and not Thunderbird. Though Mail still has its little “episodes” with IMAP where it really can’t decide what it’s doing…
Keep up the good work!
Tom