I think you SHOULD use them any chance you get, but ONLY for things that will visually enhance the page for visitors using more modern browsers. That is, they aren't REQUIRED for the page to look correct in older browsers. This is the theory of "progressive enhancement" / "graceful degradation"

Many CSS3 features are poorly supported in most browsers because CSS3 itself is still in working draft, so its not known which feature-set will make up the final version - so your chosen implementation might be completely unsupported in the near future. Feel free to use CSS3 properties but be warned that their interpretation by browsers' may change over time.

Thanks for the kind comment! No, I don't run any web design classes - but am in the process of producing a series of online web design tutorials. This is a personal project that I am running in my spare time, so I don't know when I'll actually get around to publishing anything.