If it's going to be a GNOME app, yeah, you should probably use GTK+. If I were doing it, I'd do it in Perl (there are GTK bindings for it), but seems like a
lot of these are written in Python these days.
There's a good
online book for GNOME/GTK development written by Havoc Pennington.
I agree, it's not entirely clear to me why something so fundamental is still not a solved problem. I know that it's not particularly sexy and so doesn't attract very many developers, but it's a big enough itch for enough people that it should be scratched. Probably the most productive approach is to find one of the projects that is trying to tackle it (like maybe
smeg, referenced above) and try to help out there.
BTW thanks foolish for the pointer, I'm going to give it a shot this weekend.