Garmin Edge 810

Three years after getting this unit I'm still discovering functionality I wasn't aware of and new ways to tailor my user experience. Use this for commuting, for road cycling and now for navigating trails and am routinely delighted by what it can do

Pros
Highly configurable, automatic upload, simple to use

Cons
Occasional system crashes after long rides resulting in lost data. Can be a bit fiddly to manipulate the map

Great piece of technology, and easy to sync with other apps.

Pros
The programming is easy and accommodates multiple bike and multiple riders.

Cons
The screen is a little small.

If you're thinking about the 800 or the 810, go for the 810. Just do it.

Pros
Reliable, accurate, great battery and some awesome functions, it's easy to get lost in customizing your own screens to your liking but with some pretty neat results, and the Bluetooth/Ant connectivity is ridiculously convenient.

Cons
Price is high, but worth it if you want a reliable GPS; I have heard of instances of the Maps SD card becoming corrupted with no known cause, but easy enough to replace

Absolutely. Not worth buying if you have an 800 (From comparing with friends), but if you've got a 500 and considering making the jump go for it.

Pros
Faster sync times
Easier to use
ability to add Open Streets Maps
Bluetooth connectivity for live track (So my lady can check in on me if needed)

Cons
In certain conditions it can be hard to read, but once you figure out the back lighting and brightness settings it makes a world of difference.

Definitely recommend. Don't spend the money, unless you are prepared to buy maps as well.

Pros
Great GPS! Works well. It tracks your ride, calories, pedal revolutions, has maps, and keeps track of speed, laps, lap time, and much more.

Cons
None