I installed v.6 yesterday, when I learned that the final release was out ... so far no problems, but my clock-sync application (WebTime, from Gregory Braun) then refused to connect to any of the remote servers, giving me a "non-existent socket" error message each time I tried. I'd been using it for years (no updates available for ages now, so quite possibly some of the servers' addys are out of date, but I wouldn't have thought NBS in Gaithersburg would have changed their IPs).
Uninstalled that one and replaced it with SP TimeSync, which works just fine. I'm guessing that v.6 made some changes to how its proxy works ... even my PCTools firewall warned that the avast service "seems to be acting as a local proxy" and ask me to OK that, something I'd never run into with previous versions.