I'd like to second the last posts response. Almost every site I do, the description tags are used in the search engines. The key is that you have unique descriptions for every page, and that the description is on target with the page content.
I can point to tons of pages on one of our sites,
www.promarktech.com that all use their descriptions in the search results.
The key is not duplicating the same page description, and making sure you have the tags closed off properly and so forth.
Also, on the "keywords" only side of the fence. The actual "keywords" meta tag, in my opinion has actually been reduced in overall value. On target unique "descriptions" have been raised in value.
Dburdon says it most eloquently.