It depends on how the route is actually stored. If it's just a list of waypoints, reversing that shouldn't be too hard. But I don't actually know how the route is stored, so I can't say if it's possible - that's why I asked. Even a button to calculate the route both ways would help.

Another annoyance I've found is that if you tell it to download a route, it does that full time, and it's not possible to cancel it. I accidentally tapped in slightly the wrong place this morning, and it has been downloading a route for over an hour - a route I had already downloaded anyway. It just freezes, and won't do anything else until the download is complete, and it's not possible to cancel. Having it check for other input would be very useful.