I got this unit as a re-manufactured item. It was a very good price and functioned ell, but there are some things I didn't like about this one. The unit is very slow to operate with the touch screen, and the screen itself is made so that about half of the brightness is lost when I use my polarized sunglasses. If I rotate my head 45 degrees to one side, the display goes totally dark. 45 degrees the other side shows 100 % bright.
The advanced mapping function was not as useful as I had hoped. For what it does on-the-fly, it is cumbersome and most of the things I'd want to do with it can be more easily accomplished on my iPhone map.
This is the first stand alone GPS that I have owned. Previously I was using the free version of Strava on my phone. I love the turn by turn navigation and that it syncs up with my off brand cadence and heart rate sensors.
This is the first GPS bike computer I have owned. I always got by with a speed and cadence pickup to the display on my handlebars. This is so much nicer with so much functionality. It was a "refurbished" unit, but it looks brand new and I haven't had any problems with it. Not looking back....
I tried it twice but I didn't like the way to change the pages. I had to do screen swipes which didn't work well specially when wearing a glove. I prefer in this regard the 520 and the 530. I didn't see that the 820 offered any advantage over the 520. About the same size. It worked well when I didn't try to flip pages or change function.
Pros: Mapping is nice, can configure the pages to your desires. Can setup multiple Bikes. Syncs easily. Has features to show text messages and phone calls. I got a NHO version so the price was fantastic on sale
Cons: The batter life is not nearly as good as my 6 year garmin 800. I'm slow but go long - this is gonna be an issue for me in the summer months. I also wish the device was a little big larger.