This is mostly cheap shot journalism. Sure, there's lots of free software out there with awful interfaces. But there's equally a ton of commercial software that's bad, and for many of the same reasons. Take a look at the crapware installed on any new Dell box, for example.
It's true that at the very high end, the "polish" of commercial software is better. There's no free equivalent to, say, Apple's release and UI artwork processes. But that's not strictly a "usability" critique. There's plenty of beautiful-but-clunky software out there.
He doesn't even really mention apple once in his article. He clearly loves most things apple, but he wouldn't hesitate to criticize apple if they do silly things.
Its much more convincing to criticize his argument than just him. He makes a strong point - Software interfaces only are as good as the head guy in charge cares about. So if the head guy doesn't care much about the interface, the interface will suck even if there are great designers working on the project.
I'd say that open source software often has medium to poor interface quality is that making software look good takes a lot of time and has to be done by someone with design talent. This isn't usually the case - usually the lead programmer decided how it would look from the beginning, or just copied some other software.
If anything, open source software is usually decent because they most often just copy some commercial piece of software - which is usually decent. In the few cases where they get creative with the interface (like the gimp) it can come out half-baked because they don't spend enough time evaluating the usability of the design. (not that the gimp interface is half-baked).
You know, I just don't see it. Maybe it's because I'm a developer, but I just don't see that many usability problems in open source projects, and these articles are going out of their way to avoid giving concrete examples. I'm marking this (the MPT article) down as Microsoft propaganda until the "interface design experts" start pointing things out.
It's not like it would be hard. Configuring Xorg makes me cry, and CUPS was still no walk in the park last time I checked.
I don't see many problems either, probably because I am a full-time GNU/Linux user, but another application that is often pointed out as difficult to use is The GIMP.
I actually disagree with the premise that GIMP is hard to use, and find it quite intuitive for basic operations; most critiques actually complain that it doesn't have the Photoshop look&feel.
It often boils down to the difficult task of discerning usability, intuitiveness, efficiency, and familiarity.
Actually, I do have trouble with Gimp, too. I have to google how to make a straight line every time. Choosing brushes and changing the color are a pain, too. But I don't use it often, and about half the time I'm using it where I would have used MS Paint when I used Windows. There's probably a toy program somewhere that fills that gap, and I just haven't bothered looking. Maybe I should pick up Xfig.
As I recall, Photoshop doesn't have a line tool, either; you make lines with the brush tool and the shift key, just like in GIMP -- or you use the vector tools.
For people accustomed to basic painting applications that provide all manner of circles, lines, and squares, it comes as a surprise that such tools are so buried in Photoshop or GIMP. But it turns out that drawing lines is simply not that important for most Photoshop users, since lines aren't that important for photo touchup, creating web graphics, or digital painting. For line-heavy art, there are better tools like Illustrator.
The problem is that GIMP is tasked with replacing both Photoshop and MS Paint on the Linux desktop. The hidden assumption is that since Photoshop is more "powerful", its feature set is adequate for typical MS Paint tasks... which is akin to assuming that Linux doesn't need a word processor because TeX is more powerful.
I wonder if the recent resurgence of Apple will have a positive effect on the usability of the entire software industry. With so many geeks using macbook pros, it's only a matter of time before that aesthetic finds its way into more open source projects.
It's true that at the very high end, the "polish" of commercial software is better. There's no free equivalent to, say, Apple's release and UI artwork processes. But that's not strictly a "usability" critique. There's plenty of beautiful-but-clunky software out there.