I tend to agree with ArtzGirl. How much description you use is often a matter of style. Of course, I also agree with Dana and Hubpage Girl in so much as the reality that rich and deep description, which often means lots of it, is very helpful to writing. As a writing teacher, I can also suggest this is true in regards to the fact that most beginning writers--especially middle school kids--don't use enough.
Still, I think you can go overboard. I absolutely love the novels of Victor Hugo, but 50 pages describing the city of Paris from the top of the Cathedral of Notre Dame in The Hunchback of Notre Dame and 100 pages of describing the nunnery in Les Miserables was really unnecessary!
The truth is that the right amount of description is the amount that best serves the purpose of the story and gives the reader a rich, varied and vivid experience. Since purposes vary so much, as well as readers, that's a pretty hard mark to clearly identify beyond the reaches of a particular writing piece.