When Should I Go For HTML5 & CSS3?

Question

There is a lot of buzz about HTML5 and CSS3. How do I know that it's time to get started with them and use them straight away in my projects or how far are we from using them?

Update: I don't want to apply the rules of:

Graceful Degradation
Progressive Enhancement

I know if this is the case, then we can use them today.

Answer 1

When can I use...