I wholeheartedly agree with all of that except GIMP. The UI in GIMP is horrendous and the only reason it's successful IMO is because the gap it fills is that of an expensive and confusing product that is niche to a lot of people who need some of the functionality but don't use it for their job.

I use it quite often (and loathe the interface) but I'll never pay for photoshop because I don't need the pro tool and after 10+ years of GIMP I don't want to shake up.