Today I came across The HTML5 test at http://html5test.com/
Visit this site and it will tell you to what extent your browser supports HTML 5. At the time of writing the maximum score is 160, but as the authors note this is a moveable goalpost as the spec is being updated.
These are my findings on Windows 7, in descending order:
Chrome 4.1: 118
Safari 4.0.4: 115
Opera 10.51: 102
Firefox 3.5.9: 100
Opera 10.1: 38
And the trusty Nexus One? Joint top at 118
So how ready are we? Getting there, it looks as though the browsers who release frequent updates are working on their HTML5 rendering – see the huge leap seen in the recent Opera release. Sadly, it looks as though it won’t become mainstream until IE8 dies. Seems to me that IE8 is destined to be the new IE6, just give it a year or so. Presuming IE9 supports HTML5 of course.
I’ll update this page as the browsers get updated. Post your scores in the comments along with Operating System, Browser and Browser version and I’ll add to the list.