Just a word of warning.... as with any firmware update (phones, etc.) there is a risk that you may render your device useless. I attempted to update my SMH10 ealier this month (to v4.1.1 - not a beta) and managed to brick it. ie. it was as functional as a brick. It's now winging its way back from California after SENA fixied it under warranty. Cost me a) shipping, b) time, and c) stress.... particularly with the rally coming up. I was lucky to have bought a dual set. I think it was some driver incompatibility with Vista (yes - I need a new PC).
The primary reason for the upgrade was to better support the phone/music interplay with my new Garmin GPS.