They do a bit, mainly in the upper inner quadrant, but I guess it depends on how tall you are, how high you sit, and how you have your mirrors adjusted. After I installed them, I adjusted my mirrors slightly, as they were visible, but for me, not too obstructive.
Here's some photos that might help:-
Left hand mirror is a bit high, but this gives you the idea. RHS is a bit out, but in use, you can just see the bottom of the barkbuster.
I still haven't had the chance to ride any real distance, but with winter gloves, cold fingers will be a thing of the past. Will try and get the time on the weekend, pending half decent weather, but I suspect that with reasonable gloves and heated grips, there is a setting that would be between roasting and warm that will suit.
Heres a few shots showing what they look like....not the best, but not as doofy as most mitts or muffs, the handlebar type....
Apart from how warm they keep my hands, the thing I really like about these is that they are open at the back and all the controls are easy to see and access, even my MCC control. The peg type throttle lock I still have installed touchs the top inner surface when in use, but it's still useable as well. Real happy so far, but will hopefully get a very cold ride in to give them a torture test soon. Just that I'm getting a bit soft in the cold now.