Sena SMH-10 Bluetooth Headset
I started off buying this as a gift for my father-in-law. When he sold his bike, he re-gifted it back to me. Prior to the re-gift, I bought myself the SMH-5, which is the smaller version of the SMH-10. Without going into a full review of the SMH-5, I really liked it too. The only complaint I had about it was the CRAPPY speakers that came with it. However this could be easily remedied by buying the SMH-10 speakers for the SMH-5.
But, back to the 10...
I really like this headset. It allows me to listen to music and audio books while on the road and even (gasp) make or take a phone call. While I'm sure someone out there just had a minor coronary about me admitting to using the phone while riding, I really don't think its that big of a deal. I pair the SMH-10 to my Garmin 660, and it really makes it easy to deal with the phone and audio.
Since I've had the SMH-10, there have been 5 major firmware revisions, the most important of which was bring voice prompts. (Prior to that, you had to decipher a series of beeps and boops) Audio quality is very good, as long as your are using the A2DP protocol. If your device has to use HDP, its going to sound about like a phone call.
On a long distance rally, I ran into a slight problem regarding battery life. It only lasted for 12 hours. For any normal person, I think 12 hours would be way longer than necessary, but I managed to max that out. My solution, as of yet untested on a rally, is a second SMH-10. On Amazon, you can buy only the control unit, without a second set of headphones, mic, etc. I've paired both headsets to my GPS and it seems to work swimmingly. I'll update this after I've had experience on it during a rally.
Another slight problem I've had to work around is the boom mic. I use a Shoei NeoTec modular helmet and I haven't found a really good way of mounting the unit so the mic isn't awkwardly fished under the chin of the helmet. Its definitely not a deal breaker, but its sort of a pain all the same.
Bottom line. Go buy one. Well, buy two.
UPDATE: Yeah, the boom mic is a major pain in the rear with the convertible helmet. Luckily there is a different base that allows you to attach the boom mic to the inside of your helmet.