Broadly...
...MS are correct. To a retailer, the majority of their customers want Windows. However to put plain wrong values on the cards is, well, plain wrong.
Currently MP3/camera/printer support is fantastic for Linux, with many devices working straight out of the box with the drivers in the kernel. Does that count as "few"? I think not.
Disclaimer: My main OS in Windows XP, though I dual boot Ubuntu 9.04. I run a webserver on Ubuntu 8.04, and am upgrading my windows install to Windows 7 soon (I would have waited 6 months but it was less than half of the retail price!).
I also work in a retailer part time and am rather used to these misleading material from suppliers. I am lucky enough to know when what I'm reading is wrong - many of my colleagues are not.
Getting my coat because I never thought I'd comment on a Linux vs. Windows comment article, it's just two damn infuriating reading all the closed-minded arguments (on *both* sides)