Yea, I bought a set of the Senas last week and installed them in my and my GF's helmets. Not really impressed after coming from the top of the line J&M headphones, sound quality-wise but we'll see once we road test them.
Nick, I'm surprised that the unit knows the difference between your GPS and your phone... BTW why don't you just use your phone for all three? j/k
I have a similar problem, as I have a GPS, radar detector and phone. I don't trust BT with radar alerts so I have mine wired to the headset 3.5mm with a splitter that puts the GPS on the left and the radar on the right.
I can listen to music off the GPS in mono if I really want...