whyeyebike - this is indeed my first garmin. i nearly bought an edge 705 several times in the last two years then heard about the 800 and edecided i'd pull the trigger as soon as they were released.
i know garmin gps devices have a reutation for bug/poor software but so far the garmin 800 has exceeded my expectations.
the only issue i've had so far has been the navigation missing a couple of turns - the route has been right but it didn't prompt me to turn. i think this is due to me creating routes via BikeRoutToaster (which uses google maps) then transferring them to the garmin which uses Garmin maps. I've not tried to tweak the settings or use other route creation sites yet so i'm sure there is a solution.
to put this in perspective i'm taking about missing 2 or 3 alerts in about 300 miles of riding, all on very small single track country lanes.
i love the 800 as i can pre plan a route avoiding big roads and just ride. great if you've got no sense of direction like me!