1) There's more to Chrome than Webkit + V8 + rolling version numbers. There's WebGL, there's voice input, there's websockets, inline SVG, animated CSS3 and tons of other stuff. None of this is essential, I agree, but if an app uses one of these features, it automatically gets locked out of all the other browsers that do not support them. Check out http://caniuse.com/
- it has a pretty handy tool for browser feature comparison.
2) Despite supporting MP3/AAC, Google willfully dropped H.264 support. I think it's a matter of convenience as much as a matter of open standards: the lion's share of music today is stored in MP3, and I believe it would turn off potential users from HTML5 media capabilities if there were almost no media files on the Net you could use them with.
3) Flash: maybe on Windows it ships with Flash; the Linux version doesn't. Also, I'm inclined to believe that it's mostly for the sake of security: a huge share of people already has Flash installed (usually preinstalled on their computers) anyway, so it's not like Chrome is helping to spread Flash. Rather, its support of rich HTML5 capabilities slowly renders Flash irrelevant.