I just purchased 24k topo for Southwest and when layered with Birdseye it makes my Birdseye views 3d, nearly just like you get in Google Earth. I had no idea it would do that. AND, maybe i am just lucky, but nearly everywhere we ride, the majority of the trails are included and of course Routable.
(Note to Garmin Marketing: If I had known that 24k TOPO was going to make my birdseyes 3D, I would have purchased a long time ago.)
I have been using birdseye and third party topos for a few years now. Routing was not possible with my 3rd party maps, and of course our desert and mountain runs were not routable with City Navigator North America. When I purchased 24K Topo I really did not expect many of our trails to show up, but I was pleasantly surprised.
So now I have Google Earth type 3D view AND Routable trails. I am tickled to death. Thanks Garmin.