I just found out about Topofusion today, and it looks like and almost perfect replacement for a program I currently use called UsaPhotoMaps.
My only concern is that there doesn't seem to be a way to call Topofusion from the command line and have it open a GPX file to plot the points like USAPhotomaps does.
I'm a geocacher and one of the things I need to do is view multiple points on various maps quickly. I use a database program called GSAK to store the points and manipulate the data, but GSAK has no ability for map viewing. It can, however, launch other programs to view maps by writing a GPX file with the waypoints then launching the map program.
If it would be possible to have Topofusion automatically launch and open a GPX specified on the command line, that would be perfect. I'm not yet a registered user, and as this is probably the feature I'd use on an almost daily basis, I'd like some feedback as to whether or not this could be implemented. Looks like you've got a great program here, add a way to automate it a bit and it would be perfect!