Inkscape is one of the better open source UIs IMO. There's a lot to learn about vector vs raster graphics but that's not the fault of Inkscape.
Gimp took a while to figure out.
Blender has got the be one of the steepest learning curves out there though. Not that the UI for Blender is bad. It's just that there are 5-6 different sections and each section is like learning a new app. It's huge and does everything.
Are we talking about the same Adobe here? Adobe software generally does work but avoiding bloat? Have you installed Reader lately? They have their share of instability as well.