Matt Cutts made a blog about them 6 months or so ago. He stated that search engines don't exactly ignore them, but not much weight is given to them either. Meta Tags are your suggestions to the search engine as to what you believe are pertinent keywords to your content. If they are completley wrong or old tricks like keyword stuffing are used, I beleive a penalty can occur. They aren't just for SEO either. Do a search for "meta tags" on Matt's blog and you will see he talks about various things they can accomplish.
they are not so important.... but It helps in a way of snippet your page in SE. so that meta tags has a value in terms of SEO.
Think of this way....saying they are not so impotant is like saying a muffler for your car isnt so impotant. Its so easy to do, you should be in the habit of doing it everytime. And the fact that it can only improve you site, makes no sense not to do it, other than pure laziness. Your car can run without a muffler, but its loud, noisy and smelly. Your site can also get listed without meta tags, you can leave them off and the site will still run, but it will run better with meta description tag.
nowadays most SEs don't give much of importance to meta tags though you can still use them as it still helps....
Conclusion of the thread, Using meta tags properly wont harm you instead could be beneficial for certain reasons, so use them. The meta description tag is nearly "must-have" and also plays some role in search engine optimization and SERPs.