Seems ok here, just rebooted again now and no issues at all. I had a bit of oddness with Mail initially where it didn't run the rules I'd set up on new mails landing in the inbox, but it seems to have sorted itself out now. I've not tested the GMail / Virgin thing that was such a disaster in 9.0 as I reconfigured all my pfm addresses to redirect to an iCloud account at that point and have just left them there.
Any new actual features with 10.9.1?