I have the smh-10 and really like it.
If I was more sure that I really needed a bluetooth communication device when I bought it I probably would have gotten the higher model 20-whatever at the time.
I think the 20 has better range and a built in radio. I use mine mostly for listening to music on longer hauls. But also when the sig other and I ride together, both on the same bike and when on individual bikes.
The range of the 10 is line of sight and only about 1/2 mile or so. But if you are using you have cell reception your range is only limited by cell minutes or reception.
So far the Sena has worked very well and seems relatively easy to use and connect to my cell phone, other Sena's and my stand alone gps.