That post has zero real world examples of things that Vista DRM has prevented him from doing.
Remember that the movie studios maintain that ripping your own HD-DVDs to your hard drive is infringement. In the USA, describing that process to someone else is a potential violation of the DMCA. You're helping them break a protection mechanism, don'tcha know.
You can, of course, fight this stupid doctrine if you have lawyers. Software companies, universities, and some big magazines have lawyers, but random posters to Slashdot do not -- they prefer to spend their money on other things. So I wouldn't be too quick to accuse them of ignorance. The vagueness is often deliberate.
Do you hate that? So do I. I really hate living in a world in which vitally important information about the functionality and security of our operating systems is spread by samizdat -- traveling in the form of dark rumors posted semi-anonymously on foreign-hosted IRC chats by guys with names like "3l1m1n4t0r". Thank god for the occasional foreign security researcher (warning: PDF link to Peter Gutmann's talk):
http://www.cypherpunks.to/~peter/vista.pdf
(Note that these slides contain some references to the kind of "real-world" examples you're looking for... e.g. folks who can't play back their own home movies. Feel free to follow these up.)
But even professional security guys don't seem to talk openly about what they know. They get a lot of their information via quiet chats with each other, because publication is risky. Meanwhile, Microsoft can fill the airwaves with all the propaganda they want, because they occupy the legal high ground.
I wouldn't be surprised if, legally speaking, it's safer to upload footage of yourself having sex than it is to upload an honest verbal description of how you got the movies onto your Apple TV. God help us.
"Microsoft want the DRM themselves because it puts them in a position of power over their competitors. They want Windows to be the OS that can play movies and music and other OS's to be shut out in the cold."
That pretty much sums it up. No good can come of this.