I'm currently using an Edge 500, which generally works OK. However, one limitation that's a bit problematic for me is that the map view on the 500 shows the map and upcoming turn, but not your current speed.
Turning on courses on the 500 also brings up several pages, whether I want them or not. The unit also is a bit slow when running a course, so switching around is inefficient.
From what I can tell, the 810 map is the same way:
Anyone know if there is any way to have speed display with the map, or with turn-by-turn instructions? Or does the 800/810 allow me to turn off certain pages when running a course?
Here's the manual for the 810. Look at page 11 for customizing activities and data fields. I don't know if this has the info you're looking for with respect to adding data fields to the map display, but I believe it can be done. http://static.garmincdn.com/pumac/Edge810_OM_EN.pdf