I only use my 800 for MTB rides up where I might get lost, or when I know I'll be in some unfamiliar territory in a different city (like on vacation). If you don't do those things often, I'd save the $200.

I really doubt you'll see any new higher end EDGE computers within the next 2 years, so I wouldn't hold out for that. IMO the 500/800 are here to stay for a while.