CSS3 promises a whole new array of features which will give web developers even greater control over their web designs.
Still being developed, the new set of rules will be grouped into modules, both for ease of use and also to enable them to be completed independently of each other during the development and testing stages.
Interesting new properties will let you style multiple background images, image borders and gradient borders and even rounded corners. Other features include text effects, resizable elements and multiple column support.
The main problem facing web developers is with compatibility. Currently only the latest versions of Safari and Firefox 3 (beta) support features of CSS3 and it is very difficult to say when enough people will have compatible browsers to warrant widespread use for the new style rules.
I have started using some of the new features but only sparingly and for non critical elements. You should always have fall back methods so the website stylesheet can degrade back to CSS2.
I would say it is still too early to worry too much about using CSS3 on your website and the time involved in making it backwards compatible probably isn't worth the effort yet.
For more information on CSS3 check out - CSS3.info.