After doing the dev channel update there is no call issues anymore. The proximity sensor sometimes turns the screen on while i call but not a big issue.
Have not tested mms but the sms feature is snappy, I get them instant.
As the experience is very good, I can see my self daly-driving it now.
Will do more & more testing..Report / check bugs.
on a sidenote, a 'remote control IR' app would be bangers. Since this phone has an IR sender.