I have both.... Backbeat 906 (with 3.5mm jack accesor) and the Backbeat 903.... I alternate then almost every day... 1 to use it from 9am to 5pm at work, and the 2nd one to use it at the gym or when I go rock climbing...
I love those headphones, they are light, comfortable, battery life is good for the size, the sound quality is on par with wired headphones (and im being conservative I actually think the sound is GREAT)...
Also sound quality for Phone calls are very good... at both ends the call is clear and I love talking on the phone in Stereo!
My only complain is that out of the 7 hours of playback that you get the last 30 minutes are almost useless because they make many beeps reminding you "low battery" which defeats the music experience. I should have been a more discrete beep.
I would definitely recommend them, and if you have any problems let me know...
Also note that most BT headphones are not meant to be used under heavy sweating... I use them while working out, but I try to do my best to keep them dry... so keep that in mind