I wouldn't think it would be a problem with a BT keyboard, as the transmission is intermittent with the keyboard instead of steady with music.

When I've used the headphones inside (not often or much), I did't notice many dropouts. It's only outside, where the wifi signal is weaker (which causes more traffic?) that I notice dropouts, generally in parts of the yard farther from the router.

Granted, I haven't tried streaming audio from my computer to the N900 and use BT headphones. Perhaps I'll try that tonight and see if it causes problems. I'd guess it should.