I have had an 800 since last Christmas, I don't use the "routing" function that much. But I have on occasion entered a route before leaving if I have to zig-zag through neighborhoods I'm not familiar with. I find it's a little hard for me to really see my position on route (using a stem mount) but with experience I've gotten better at seeing an upcoming turn on the moving map. If you miss a turn (at least how I have my settings) it gives out a loud beep and an "off-route" popup. So you can then look down and see what you did wrong. I haven't tried to "recalculate", I just either get back on route immediately or figure out my own way back (next block maybe).
It does seem for some reason at a light the map turns until I get going again then it re-orientates correctly (track up).
I guess you also have option to set a POI on the map and navigate to it, or navigate back to start. Haven't tried that. I do know that if you load a saved course, you can tell it if you want navigation to the start point or not (or for example, join enroute which I think you have to do yourself).
I guess I could get by with a 500/510 for most purposes, but I still like having the map "just in case". I d/led the free OSM map for Hawaii which works perfectly fine for me.
scott s.
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