It doesn't excite me in the least because, since I can't afford to alienate big chunks of my audience, it might have enough penetration to use in, oh, 3-5 years? Meh.
While it might not be ready for general-audience web projects, I'm already using HTML5 and CSS3 features (including app cache and database storage) for some upcoming Android- and iPhone-specific mobile sites, and for a product that embeds WebKit in a non-browser application. Many of the features are also useful for building Flex/AIR/Silverlight-style "rich" apps, for which you could distribute Prism or another site-specific browser.
My gut feeling is that the mobile arena might be where html5 takes off first, with the number of webkit-based browsers out there now (iphone, android).
How does that affect you? Your HTML markup will work in HTML5, too. In any case, I keep reading no one will use it for years yet most of the leading developers and designers I know are using it today. And I'm joining them since all my markup is now HTML5 as of six months ago.
When you say that your markup is HTML5, do you just mean that you changed the doctype at the top (That's trivial, and its only real effect is saving a few bytes, though I suppose it's a nice symbolic gesture), or that you are now using all of the new semantic elements like <article> and <section> and <footer>, using <video> instead of plugin-based video, including features like drag-and-drop, or offline use of data-heavy apps, &c. &c.?
Corporate users would still need their administrators to install the plugin. But Chrome Frame could let change-fearing companies keep their users on IE6 (no retraining users or retesting existing sites), and use the Chrome engine only for sites that opt in to it.
I think part of the problem is MS encouraged people to write a bunch of ie6 specific sites. Thus, since ie doesn't AFAIK do side-by-side installs, the need to stay on ie6 for line of business apps.
Probably. On one hand, People Still Use IE6. And the people who still use IE6 aren't people who install things like Google Chrome Frame, or the latest updates from Microsoft (obviously). So for the time being, more features, along with cleaner syntax and the rest, means more work for web developers who want to use those features and whose audiences aren't particularly ahead of the curve.
On the other hand, those developers whose audiences are ahead of the curve, or who don't mind the blasphemous "Please update your browser. Here are some good ones:" link, will push the industry forward until the number of people still using IE6, or FF1.5, or Mosaic or whatever, approaches zero. It will happen because people will get annoyed, or viruses, or new computers running new operating systems and browsers. In that way html5 is the best thing that could happen to the web. A backwards-incompatible version will (hopefully) throw the few stragglers, who spend money on the web but still don't need css2, into the 21st century.
My grandmother was, until very recently, using MacOS 9 with IE4. She did not care that her homepage (apple.com, as it had been since she bought the computer) was impossible to read. People still using IE6 and even IE7 in five years will not be the kind of person who spends a lot of time or money online.
It doesn't excite me in the least because, since I can't afford to alienate big chunks of my audience, it might have enough penetration to use in, oh, 3-5 years? Meh.