I haven't used edge much, but I haven't had any issues in Firefox just yet. I did notice once though that the system wasn't recognizing that it had the nvidia gpu while the tablet was docked to the base. A quick undock/redock of the tablet fixed that (and perhaps a forced scan for new hardware in device manager might also have worked). Ahhh, early adopter bugs. I saw 'em last year with the SP3, too.
So far the only thing that has caused the fan to kick on for me is games. I ran Diablo 3 for a little bit and then hubby ran MechWarrior Online. Both ran beautifully, but I did hear the fan come on and it stayed on for a few minutes even after closing the SB and putting it to sleep.
No blue screens yet here.