I have been using the Nokia BH-505 with a HTC Hero Android (1.5) phone and a Samsung NC-10 Windows 7 netbook for about 4 weeks now and consider them to be an excellent choice for me.
The headset is generally well designed and built but, as at least one reviewer has said, the buttons for control do feel a bit cheap. The position and design of the play\pause (left) & call/answer button (right) mean that when using them you are pushing the earbud further into your ear. This may not affect users of the on-ear buds but if like me you use the in-ear buds then you will need to grip the bottom of the ear piece with your thumb to avoid discomfort, something I accomplish without much trouble. This is made slightly worse on my set as the call/answer button is considerably harder to push than the play/pause, something I hope gets easier over time.
The volume and skip buttons work well enough although they aren't designed well for use during movement as it is too easy to make an accidental input (e.g. skipping track when you only wanted to fast-forward).
The rigid design means that on my head there is about an inch gap from the middle-back of the headband and the back of my head so the band is effectively floating in the air with the headset largely supported by pressure and the hook over the ears. This may sound uncomfortable but is not at all uncomfortable for me and the only issue I have is that when running there can be movement. For this and the button design I wouldn't recommend these for very active use.
The choice of 3 on-ear & 3 in-ear buds should mean that all tastes are catered for and I have gone with in-ear as this seems to give the best sound, noise blocking and comfort for me. I usually prefer on-ear types but found these a bit irritating although the largest one will accept the little foam covers (not supplied) you get with most on-ear buds which did help with comfort.
Sound quality for stereo music playback is very good in my opinion (I am definitely not an Audiophile) with good base supplied especially with in-ear buds.
Voice calls are similarly good, the position of the mike back near your ear does mean you can't whisper but all people I have asked tell me that call quality is good and I have no trouble hearing them.
I have owned or used a few sets of bluetooth stereo headsets and can honestly say these are the best I have used. Their relatively cheap price (I paid 39 Pounds, I have used some 85+ Pound sets) makes their short comings acceptable and the quality audio performance, comfort, battery life and size/weight make these a set that I would recommend anyone giving a go.
Also worth noting that this headset has attracted a lot of attention from others who all find it to be an attractive headset to wear so you shouldn't feel self conscious about using them.