Have a few friends on the 737 and all of them (my friends, that is) use the Telex 850.
Pudoc, I use an A20 (still have whirly bits in front of the engines) and I forget that I am wearing it most of the time. Longest sectors would be ~ 3 hours often with very short turn arounds (immediate departure for repositioning) so it could be on my nut for about 8-10 hours a day and I haven't had a problem with comfort.
Battery life isn't the best, but I don't find it bothersome. I always carry a good few batteries in my bag and I get around about the prescribed 45 hours out of them.