Or whatever they are calling it. I did some reading around. Quite a few places say that we can use the doctype today and that it is backwards compatible. Like here http://ejohn.org/blog/html5-doctype/. To be clear, this question is only about using the doctype not the other new tags.

Have any of you used this yet and done any extensive cross browser testing? Are there any drawbacks that you are aware of? Thanks!