Several of us in our riding group have the Rhino 650 or the 655T and both have been working great!!!
No issues with the touch screen in the cold, great battery life, easy to use, once you just take the time and play with it a little.
The radio portion works very well, clarity and range. The mapping and being able see the other riders in your group, once they update is a great feature!! We have had several instances where a rider or two have gone "MIA" for a bit and these things completely fix this issue!!! Once they tell you they are okay, the map is updated and you can direct yourself right to them.
The GPS tracking feature works great as well. We have had a couple instances where weather starts to roll in and we're in a newer place, no problem as you can track your way right back out.
A few of the guys in our group have Ram mounts for them and the rest of us just put them into a pocket. I personally keep mine in a Skinz handlebar bag and it fits just right. Doesn't bounce around and it's easy to get to. The guys running the Ram mount also run some kind of tether but no one has had an issue with the unit coming out either.
All in all, it's a great piece of equipment that I would recomend to any backcountry rider. Not only is it a piece of safety equipment that assists with getting home safe it also marks those great places we sometimes stumble across.
So two gloved thumbs up, you wont't be disapointed!