As far as I can tell, Kindle's experimental browser does not support any touch events. It also does not support mouseup/mousedown correctly. If you tap something, it sends mousedown, mouseup, and click. If you touch and hold, it doesn't send any events at all. I doubt it supports mousemove, but even if it did, it wouldn't be particularly useful without a working mousedown/mouseup or touchstart/touchend.
Also, it does not support the viewport meta tag. Combine that with the lack of touch events, and there's no way to prevent double-tap scrolling.
There's also no way to scroll the browser chrome off the screen, which is only problematic because it takes up about 13% of the screen real estate (most of which is the location bar).
Finally, CSS transforms are a little buggy; scaling in particular tends to result in content disappearing rather than getting lighter, presumably because of poor anti-aliasing support in their display code.
In short, although the browser does a fairly good job at rendering (I think it is based on WebKit), it does a terrible job at doing just about anything with the slightest bit of interaction.
Kindle Touch results from my test tool (http://www.gatwood.net/runtests.html
latency: 2.4 seconds