Here's a review that may be of interest to those considering a Garmin 820. He talks about (and shows in a video) the problems with the touch screen and how it's very slow to respond -- if at all. I've experienced all of this many times. Also, just trying to get the unit to shut down can be more than a little frustrating as shown in the video. And speaking of shutting down -- my 820 has recently begun to shut down on its own in the middle of a ride for no reason whatsoever. I may have to reformat the unit and start from scratch to see if that helps.
Again, my 8 year old 705 is a superior unit in terms of accuracy and reliability. I never expected that to be the case when I decided to upgrade to what I thought would be a superior unit.
Kevin g