I love when videos are on Vimeo because all of their videos play natively, and when I click on a YouTube video, I'm always hoping that it isn't one of the Flash-only videos that I need to switch to Firefox to watch. HTML5 might be in its infancy, but it already sucks a lot less than Flash, at least for those of us that aren't using Windows.
The issue isn't just performance—it's who I want controlling web technologies. HTML, JavaScript, and CSS are open standards that anyone can implement. Whether or not the performance is the same right now, I have way more faith in Mozilla, Apple, Google and Opera than I have in Adobe (and if they all drop the ball, someone else will pick it up). Adobe definitely has talented engineers, but they've demonstrated again and again that they're just not capable of making Flash stable and efficient. I'm not sure if this is the legacy cruft built up in Flash, a lack of interest in performance on platforms besides Windows, or just pure incompetence, but I don't care. They've had over 5 years (over 10 if you count Macromedia) to work their shit out, and they haven't.
Flash may have had a role back when web technologies just weren't up the task for displaying any kind of rich content, but that day has passed. It's telling that the vast majority of articles I've read defending Flash are written by people who directly profit from Flash continuing to be a relevant technology. Some are Flash evangelists, others are just people who decided to hitch their careers to Flash and are just now coming to terms with what a bad decision that was, and a few just plain don't understand what they're talking about (e.g. Dave Winer). This author isn't one of them—he's actually provided a reasoned argument, and the awesome CSS3 stuff he's been putting out shows that he's not just blindly defending the only tool he knows—but people like him seem to be few and far between.