+1 on the Sena. I also invested in the wired mic accessory in order to ditch the boom mic. I don't use bike-to-bike, but I've paired it with both the GPS and the Phone (Droid) and it seems to work just fine. Frees up a ton of room in front of the chin (Shoei Quest is my helmet)
Additionally, the speakers can be used (ie. paired with the GPS) without the mic attached for those rides where you just want to leave the phone tucked away in pocket, which is actually the primary reason I picked it up. Only on testing and multi-day trips do I plan on having the mic/phone pumped through my helmet while riding.