Before I start the post I should point out that neither one of the headsets I mention are endorsed to work with the PS3, so in theory you're taking a risk if you're buying one for that purpose. E.g. Even if they work at the outset, Sony may release an update that prevents the headset from working with the PS3 in the future. I'd also like to say that both headsets worked well (at least they did for me) for their advertised use, i.e. as a hands free solution for a mobile phone.
I recently bought a Motorola H670 both as a headset for my mobile phone and for my PS3. The H670 worked fine with my phone, it didn't work so well with my PS3. I swapped the headset for a Plantronics 320. The Plantronics has worked well with both my phone and the PS3.
It seems the problem with the H670 may be linked to Firmware update 1.6. See the links at the end of the post for references.
H670 Output Problems (i.e. when you want to hear other people)
In short, when other people were talking (either in game or using PS3's voice chat functionality) I could only hear static through the headset. I eventually configured the Voice Chat program to output sound to my main speakers, rather than to my headset, at which point I could hear the person at the other end very well. i.e. The problem was between my PS3 and the headset rather than the other party's PS3 and mine.
H670 Input Problems (i.e. When you speak and want others to hear)
Every time I said something the person on the other end complained that I sounded like a Robot and asked me to speak more slowly. I originally guessed it was a bandwidth issue, who knows perhaps it was, but ultimately switching to the Plantronics 320 solved it.
I notice that the 670 supports BT 2.0 specification, whereas the 320 supports BT 1.2. Could that have been the problem? For the time being I haven't got a clue. It is a little puzzling that Sony hasn’t brought out an official headset to date. One concern might be that Sony has a part to play in the problem I've described. If so I wonder whether any "Fix" they release in the future might ultimately "break" compatibility with headsets that currently work well.
If you have any ideas feel free to post your comments.
The [PS3] Bluetooth Headset Guide - Useful guide includes stats on headsets that successfully paired with the PS3. Doesn't go into details on other types of problems.
Firmware 1.6 Problems - Various people discussing headset performance before and after Update 1.6 was released.