Thanks. I actually hope to hide all the browser differences by using jQuery, so that is not my main concern. I worry more about user experience and overall responsiveness of the game.
Now, if you go the Flash route, which should I pick: Flash or Flex? I see that there's also Adobe AIR, but it doesn't seems to be suitable for gaming. Or can I combine Flash and Flex together somehow. I googled a lot about this but couldn't find any tutorial that is up to date. Everything that is complete is written like 5 years ago.