I am finding it hard to hear while using the 640 with my Q. It's like I hear the caller - then their voice fades a bit - then comes back etc... I'm starting to think this may be a known issue with the 640 and Q - since my 640 worked fine with my 6600.

Ex - Trying to find an example - closest I can come up with is when you are watching TV - and one channel is much louder or much softer than another... and you have to keep adjusting the volume... that's what if feels like when I'm using my 640 and Q.

Note - the 640, Q and Audible work great - no fading of sound etc...

I would really like to find the answer to this question as well. I have tried a lot of different bt headsets from moto to jabra. It seem everyone I try has this fading problem, however if I use my Samsung i730 then there is no fading. I am about to go our and try yet another BT headset (I have enough to open a store already). I am thinking about the Motorola H700. I really like the Q and this fading problem is the only thing keeping me from using it on a regular basis.

Jordan - I'm finding that the fading comes and GOES - I have tried several different set's... to date the only one that NEVER fades is the LG HBS-110 stereo BT headset. It sounds great - but not a good replacment for an in the ear BT -great for the gym but too bulky for every day IMO.

Also - with the 640 I am finding that with some calls its very good - others I tend to get the fade. I'm trying to determine if its on the Q side -- or the person that I'm calling.

I have the 645 and have no issues at all using it with the Q.

I have the Moto 700 Headset and it works great with the Q. The only time I notice any fading (and this doesn't happen every time) is when I check voicemail. Other than that, the sound quality is excellent. I also have around 8 BT Headsets laying around. Good luck.