I bought the 810 last year because I was riding longer than my iPhone could hold a charge while using a cycle navigation app. With the Garmin, I like that I could design routes on my computer in advance and upload them to the device. Navigation seems to work fine but sometimes if I have to take a detour it goes all wonky and seems to force me back to the point where I got off the course rather than continue from the point I get back on course.

As I've gotten used to my preferred routes, I actually use the navigation less and less and find that I'm more interested in my speed, distance, grade, cadence, etc. as I try and continue to improve my performance.

I also like the live track feature linking the garmin to my iPhone and allowing friends and family to track me live during a ride. I often ride solo, which can be dangerous and I have at least some comfort knowing that if something happened, they may know where I am. It also keeps my iPhone battery fresh so that if I need to make an emergency call it's not dead. Other than some minor glitches with syncing/connection errors every so often, it works pretty well. Most likely my old iPhone 4s is the problem, not the garmin.

Lastly, I have it set up for all my bikes so it's super easy to swap it between them versus having to have bought separate cyclocomputers for all of them. Just had to buy extra speed/cadence sensors.