Coding Horror has a post today with a title, “Don’t Ask – Observe”. In it he documents how if you ask a user what features from a set they want they will tell you they want them all. Technically he cites a “digital device” and when asked to chose from 25 features most people wanted about 80% of them. However, in using the object with all those features they longed for the simpler object.
You should read the article because it’s a very good analysis of user interaction design and why you shouldn’t ask, but observe the users using various versions of a product, be it a web site or an application.