I've been tinkering with HTML5 for quite some time though not lately. O'Reilly was surprised by how much you can use in modern browsers today, or at least by the end of June. Of course, even though Microsoft chairs the HTML5 group and vowed "strong support for HTML 5 in IE8", O'Reilly noticed this comment by a Google VP:
Developers are heading for a nervous breakdown! Reading the W3C's List of Differences is pretty shocking.