Jeff Croft:

  But I think there’s actually a very good reason
  why we should, in fact, embrace the term “HTML5”
  as an overarching buzzword for this latest round
  of web standards and specifications. Our industry
  has proven on several occasions that we don’t get
  excited about new, interesting, and useful technologies
  and concepts until such a buzzword is in place.

Source: http://jeffcroft.com/blog/2010/aug/02/term-html5/ via http://www.zeldman.com/2010/08/03/html5-fuzzies/ (there is a term HART proposed in comments, I quite like that one).

HTML 5 != -webkit-proprietary extensions.

"Instead of animating standard CSS positioning properties like left, use -webkit-transform instead."

Sigh. http://www.alistapart.com/articles/prefix-or-posthack/

Interesting article. I'm not opposed to vendor prefixes by any means. Instead, I'm merely pointing out that the title is misleading. A -webkit CSS extension may at some point make it into a blessed spec, but describing it as HTML 5 in action is inaccurate.

First of all, there are also -moz-transform and -o-transform. Second, and more important:

http://www.w3.org/TR/css3-2d-transforms/

http://www.w3.org/TR/css3-3d-transforms/

http://www.w3.org/TR/css3-animations/

I don’t think you can look at HTML5 through the is-in-spec/is-not-in-spec glasses. It’s just not a very useful distinction (the spec is just moving too slowly for that to be practical).

Indeed; I think the best way to define "HTML5" right now is "a large web-developer wishlist for near-future browser features." It's not a standard or anything (other than the part of it that's actually about the HyperText Markup Language v5); it's just a bunch of stuff that's getting hyped so much that all the browser makers are paying attention.