I have a pair going into their third season. Battery life has been good. Need to make sure you shut it off manually between rides.
I had some issues with volume fluctuations and an occasional cross talk where my radio plays in my partners ear piece during a conversation. Short tem fix for each issue was to re-boot. Eventually these were both taken care of by Sena under warranty. They are a little hard to get a hold of. But once I got a communication going it was only a matter of a week to 10 days before I had TWO replacement modules.
Regarding bike to bike, they work great as well. I am guestimating but about 200+ yards between riders. But you must have a clear line of sight for the longer distances.
I do not use the blue tooth phone or gps, but a buddy does and they seem to work well for him.
Overall, I rate them very good to excellent and Sena has been very good about taking care of any issues.