One feature I am excited to start using is border-radius with CSS3, not of any importance but highly awaited! The new html5 doctype declaration is so much more simple to work with too. Personally I prefer a less dependent upon other services approach to my work unless otherwise specified by the clients requests. However as Jake B mentioned... html5shiv and Modernizr are good tools to get started with html5.

It's still great to see designers and developers from all over the world making good use of the new features included.

That Adobe Expressive Engine Web looks very resourceful, much appreciated!