The interesting bits since the 1st preview (for me, a web developer) are:
More CSS gradients
Async script tags
Drag and drop and File API
More HTML5 form stuff
CSS3 text shadow
CSS3 animations and transitions
Regarding XP support -- I hope they never support it. I really wish the OS would go away. They do support WebM today, just install the codec. Presumably if you have Chrome on your machine, WebM will work with IE (I assume Chrome installs the codec). Given that IE is not open source, you will almost certainly never see a public bugtracker.
It was plenty good 6 years ago, but time marches on.
Rendering speed didn't seem much different than 9 and slower than Chrome 12 for me; not by much though. Now adays it seems all these browsers are rendering at insane speeds given what they could barely pull off 5 years ago.
I love the browser wars.
Also, great list of polyfills available at the Modernizr github repo; https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-brow... .
I know a few (non-technical) people who are happy using a "choose file" dialog but would really struggle performing a drag and drop: opening Explorer, navigating to a folder, resizing Explorer and the browser so they're both visible on the screen (even fewer people know you can drag files to the task bar to activate another window) and then dragging files to the drop target.
IE 10 only fails 7 tests compared to 200 for Firefox 5 out of a total of 10000 tests.
I don't use Opera, but according to this page http://en.wikipedia.org/wiki/ECMAScript Opera lags the other browser and fails 3000 tests. Does anyone have Opera and willing to run the conformance test here: http://test262.ecmascript.org/
Tests To Run: 10935 | Total Tests Ran: 10935 | Pass: 7061 | Fail: 3874 | Failed To Load: 66
The fast majority (80%) of the error log appears to be in section 15.2.3, with half of the rest also being in section 15. This would imply that around 1/3 of the entire test suite is just in that section of the specification; as the test itself describes, its coverage is currently incomplete.
Overall, I have to say, I am a huge fan of having these thorough tests come to web standards. So that browsers can't just say "We support HTML5". I am really tired of the buzzword nature of standards recently. Hopefully, this will get all browsers to step up their game.
But all the other advanced browsers, Chrome, Firefox and Opera will (with hardware acceleration).
(oh and Microsoft forced an OS update yesterday that installed .NET to the useragent in Firefox, AGAIN)
Now, how about WebGL and WebM? Eh? Eh? Eh. Oh well.
Also, it was via this release that I learned about the .exe.local directory. There is a "iepreview.exe.local" directory which evidently supersedes the DLL search path (and that is probably how they are able to package all the render engines in a "live" copy of Windows).