I bought a set of these just over a year ago and my wife and I love them. Works flawlessly with our Droid Xs. I load all my music onto the phone and sync it with the Sena. Incoming/outgoing phone calls overide the music and the intercom overides both music and phone calls.
Purchased the optional helmet clamp kit with the earbud jack/boom mic so I can eliminate almost all road/wind noise while listening to my music or using the phone. Most of my friends have no idea I'm cruising at 70+ when I'm speaking to them. Control buttons/knobs are simple to use even when wearing heavy winter gloves.
Don't have any experience with the Cardo Scala or J&M stuff but I can definitely recommend the Sena. The positive feedback I encountered when researching the Sena made me choose it over the others and I'm very happy I did.