It my new iMac takes 7+ seconds to wake from sleep (my 2002 iMac still wakes up under 1.5 seconds);
Syncing with Nokia 6021 doesn’t work (better: the sync works, consecutive resyncs fail) (this *did* work in 10.5);
Sending SMS messages from Address Book vanished (ok, this vanished already in 10.5);
Background command (⌘) click on iTunes’ play/pause button doesn’t work anymore…
iTunes doesn’t accept images from Safari dragged to the album art dialog boxes anymore…