Meta Descriptions have always been important especially for the Google and Yahoo ranking algorithm. But as Google and Yahoo have officially announced that they will not be using Meta Description for their algorithms do you need to worry about them any more?
The answer is YES. Google will still generally rely on this Meta Description as the snippet that they display when your site shows up in the search. Sometimes it will take random text from your page but in general it uses the meta Description.
So you ask so why is this so important? The answer is this; Google is now personalizing everyone's searches not just those that are logged into Google account. They do this with the web history cookies. So if you search on some particular keywords and click on a particular website a few times Google will then keep this information for the next time and then put that website higher in your customized search results. So if your meta description is interesting then your site will get a more clicks, more clicks means higher in that persons search results and since everyone's is getting personalized search results; the effect on your Google ranking could be huge.
So make your Meta Description informative and targeted to your market so that they will click on your site and therefore effect your overall Google ranking.