Several months ago I purchased a Gamin Montana 600. I got the Montana primarily because I wanted a handheld unit that had marine capabilities. It turns out the Montana is quite an adaptable GPS - I've used it with the boat with the marine mount, in the car with dashboard mount, and for hiking. It also has some aviation functions but I haven't had a use for those. See the Garmin website for a list of features. I have a Garmin 800 but thought I would try the Montana out with the bicycle since it will work with the cadence sensor and the heart rate monitor and Garmin makes a handle bar mount for it. It also has a built in profile for bicycling.
On the plus side, it has a much larger screen: 2" x 3.5" versus 1.5" x 2. On the minus side it weighs about 200 grams more. Both the Edge 800 and the Montana use a touch screen interface. The Montana also works with Gamin connect just like the 800 does. The only thing that seems to be missing is the calorie burned information which I thought was pretty much worthless anyway. I also don't think it will work with a power meter (which I don't have). You also have to buy the temperature sensor separately (it is wireless, so you can mount it wherever you want on the bicycle).
I've ridden about a 1,000 miles with it so far and my verdict is that if you don't mind the extra weight you can get a unit that works as well for bicycling as the Edge 800 with a much larger screen and that you can also use for a lot of other activities the Edge isn't very well suited for. They are comparably priced.