For one of my sites Rich Snippets provides me with a picture in the Google SERPS as well as two additional lines. That has to be good when much of the competition do not use Rich Snippets.
Mind you, if Google use it seriously then many smaller websites will increasingly be left behind because it's not that simple to implement
Bing Dude also reckons that Bing will be using Rich Snippets in the not so distant future.
If you're not using Rich Snippets to the full at the moment then my advice is to do it now.