From time to time I check html5test.com for what is new and nice....

The HTML5 test - How well does your browser support HTML5?

BB10 seems to be the leader regarding the feature completeness for html5. Not bad !

The test ist not a speed test however. It only checks a browser against the html5 specs.
l

i know a dev that have compared it with other sites on dev alpha and it still kicks the pants on other devices

Flash support is nice too

I never thought, I will be exited by BB10, but, since my 9700 now has a defect speaker, and, RIM offers the sidegrade to the Blackberry 10 Server for free, I will get one of these phone as soon as they arrive here (which most likely will be here in Germany with a delay of several month - thats a real pity).