A few reports have been posted to the announcement thread for this release of WinAVR. But, as I understand the feedback, it seems preferred that discussion of issues be separate from the announcement thread. Thus, a new thread is started.
Issue: Support for ATMega644P is mising from avr/include/sleep.h. Support for the 164P and 324P is present, but not the 644P. Should be a one-line fix.
Edit: Bug report posted on Savannah