Me and two others had the Sena 20s (their top of the line) for about a year or so. They worked great for individual use, such as listening to music and getting gps audio. We ended up all getting rid of them because they dropped out constantly. Sena was of no help and told me that drop outs were considered normal, even if the two riders were all within 30 feet of each other and riding through open farmland with no other sources of interference. It got to be such a distraction to wonder if the headsets were connected, because whenever people aren't talking you have no idea if the headsets had lost connection. Long story short, we all got Cardo Packtalks and have been incredibly happy with them. They have never dropped a connection, and their ability to automatically connect people whenever they are in range is fantastic. On top of that, they are waterproof and the Sena units are not. If big range is important to you, you should know that neither the Cardo nor the Sena units get anywhere close to their advertised range. If you have a reasonable line of sight to the other rider, you should have a connection, but it doesn't go more than 1/3 of a mile probably.
Any other questions, let me know!