Back from the first testing I ve got the following to say:
At first, game is still running ok (no massive problems noticed so far). With a screenresolution of 1920x1080 and all detailsettings to medium (grass off, all other things on) I flew over london.
There is no massive framedrop, but it is not running smooth "as silk" looks like litte micro stuttering. As I have got no AMD/ATI graphics card, I ve no graphical issues, running @fullscreen mode.
Then I went to MP. Seems like there are some performance issues now. I noticed the game stutters, when a new message in the chat window appears. Also it is stuttering from time to time (for no considerable reason...)
As some of the other posters mentioned, the radio is still not working, which I found annoying... please fix it

.
Will test again in the evening.
Greetz