I am using a sennheiser mm200 to play music and make calls. There are no issues connecting, making calls etc.

The only bug I see (software related): when using the headset controls to change songs and using the browser in full screen mode, the browser address bar will show up (URL is blank) and disappear after about 3 seconds.

The headset is able to produce excellent sound quality but when using it with the N900 music quality is average because of the missing equalizer.