The proposition "software X has comparatively bad usability" is expensive to provide additional evidence for. The existing evidence includes the typical experience of people new to FOSS using things like Emacs, VIM, Gnome or GIMP, a difficult-to-explain preference for proprietary software among professionals in various fields and among typical consumers, each person's individual experience, various critical analyses of free software by usability experts studying the problem, and sundry other evidence. If this isn't enough to convince you that free software broadly has comparatively poor usability, the odds of discovering additional evidence that would convince you is probably too slim to be worth the effort. But it's a premise many of us accept. For those among us who do, blog posts like this provide some insight.
The existing evidence includes the typical experience of people new to FOSS using things like Emacs, VIM, Gnome or GIMP...
Bad usability and a high learning curve are not the same thing. A high learning curve is what makes people "new to FOSS" have difficulty with emacs/vim, not a lack of usability.
And Gnome is also a bad example, since it is both usable and has a minimal learning curve. At my last job we set up a crowd of 30 fashionistas (no tech background whatsoever) using gnome with no real issues. Several of them also used inkscape with little difficulty.
Try to change font faces or default frame parameters on Emacs. You could describe that catastrophe as a high learning curve, but I think it's a usability problem. This is just one example.
OK, maybe you are right. I just never saw a critical analysis of free software by usability experts. I mean, I have seen analysis of some free software that has bad usability, but the premise "free software has poor usability" with some of the arguments used in the article, at least for me, implies that most free software has bad usability.
I know GIMP, Emacs and VIM may be in that field (although I do not agree particularly with Emacs and VIM), but there are so many free software projects used everywhere, and these are just examples; you cannot generalize from that. There are also plenty of examples of free software with good usability, and I have never seen a broad study of different free software to study their poor usability.
