Sencha Labs does a good job of putting HTML5 browsers through their paces.
As I was, they're quite well impressed with Mobile Chrome, but have already found some things lacking. This quote just about sums up my feelings on the subject of compliance versus real-world performance:
"As we’ve said many times previously, many mobile browsers do well on the checkbox tests like Modernizr, but fall short when it comes to real world applications and content. (In some cases, mobile browsers have even reported support when none exists.) So for real world testing, we use a collection of our own favorite HTML5 sites and demos.
First up, the new CSS properties for mobile content. On our HTML5 wish list for 2011 we asked for high performance position: fixed. And Chrome for Android delivers. For simple pages, Chrome for Android does a top notch job of glueing fixed position content to the screen. Fixed headers and footers for simple mobile optimized pages are now easily implemented without having to use a framework. However, the browser struggled when trying to maintain fixed positioning on more complex pages, particularly when combined with pinch/zoom. We saw poor frame rates and occasionally content disappeared or was misplaced. Happily, the very new
-webkit-overflow-scrolling: touchproperty, which debuted in iOS 5, is also now available in Chrome for Android. It’s smooth and fast. (Nice job Chrome team!)"
See the full report here: