My one or two cents: I
have done professional work in GIMP, plenty of it. And certainly, this or that could be better thought through, and more smoothly laid out. But on the whole - and being accustomed over the better part of twenty years - I don't quite see the major problems everyone is on about.
The Photoshop thing, on the other hand, on the rare occasions I am forced to venture there, strikes me as a confusing mess that I'm always happy to leave behind as soon as possible. Plus of course it requires one kind or another of strange proprietary OS in order to function.
