I got out on the Bike after installing one of these:
My HJC helmet came pre-set up for the HJC bluetooth system, but I went with the uClear one. uClear sold a ton of tactical comms systems to the military, and the noise suppression technology developed for this has found its way into their commercial offer. Another attractive option is that this is (as far as I can tell) the only one that doesn't have a boom microphone; rather, the mics are integrated into the speaker units. As a result, it took all of 5 minutes to install in my helmet.
I haven't tested the phone or intercom capabilities, just the music which works as advertised. Bluetooth pairs the HBC to my soon to be replaced iPhone 3GS, and firing up the music player gets music in the helmet.
The elongated, teardrop shaped main unit is attached to the left hand side of the helmet, so I can reach up and hit the button to skip to the next song (or go back to listen to a favorite again. You mount this on the left hand side of the helmet so that you can keep your right hand on the throttle, duh. I found that I had to lean down to get the helmet close to the pouch where the phone was. I'm not sure if this was because the iPhone's battery was low, or a limitation of the headset. I'll update this when I've tested with my new phone.
Works great. I'd been thinking about getting speakers to mount on the handlebars, but for $200 I got my music right in the helmet. I also have hands free phone (will test this when I get my new phone which will have better support for this - not to mention a battery that doesn't get drained so fast by bluetooth and music playing).
It also allows you to pair with another HBC headset - say, for someone riding two up. This gives an intercom capability which also sounds nice (although not tested). HBC claims that this also works with riders on other bikes up to (IIRC) 500 yards away. Again, I haven't tested this but will do an update if I get the chance.
Bottom line: even using it just for music on the bike, this is simple and works fine.