Writes Matt Cutts in his blog. Keywords are still important in the description meta tag as those will show up in the search results, though apparently not used for rankings. A video on Matt’s blog explains further as does an entry in the Google Webmaster Central Blog. The is more clarification in the Q&Q and comments that follow there.
One says leave the keyword meta tag out to save space and increase speed; another says leave it in for insurance and possibility other engines use it. Other thoughts?