This is really cool, just tried it with a recent hike ( https://cubetrek.com/view/362602 ). Strava has a really basic 3d visualization but it's from a fixed angle which isn't very useful. Being able to move around and the replay mode are really neat. I was confused a little about the flame effect on the route before I realized it was matching my mouse on the other charts.

I second the request to be able to visualize routes without timing, it'd be awesome to take some route I have planned out in caltopo and view it here.

Also it seems like not quite what you're aiming for but I already have a few places I can (and sometimes do) upload these for the sharing/community/diary aspect (strava and peakery) and it would be cool to have some sort of integration where I could visualize activities from there without having to download/upload the GPX. Maybe I really need some kind of GPX multiplexer to upload stuff from my GPS to all the different places it could go :).