...and to follow up on "Newbie"s comments...of which s/he is 100% right...

If you ask the user, they well do a "brain dump" of everything that they ever thought of that would be "neat!"  THEN, after the list is made you will find that a high percentage of this "nice to have's" will slowly become MANDATORY requirements.  This will happen quite rapidly if there is a group of customers that are "contributing" requirements since one persons "neat feature" suddenly triggers a thought from another customer, etc.

As to making the decision for the user: This has been the cause of the adversarial relationship which exists between many customers and IT.  On the one hand the customer thinks that he recognizes his problem (which might be a symtom instead) and he is frustrated by it BUT he really doesn't appreciate an "outsider" telling him what his problem is.  AND, if the proposed IT solution is wrong you can be assured that the customer will "wipe his hands" of any connection with the consequences!

Solution:  The customer MUST accept ownership of the solution (and the problem) and become a member of the team, or at least an active "spectator."  If any customer says, "Just let me know when it's done," this should be your clue that you can assume that there will be LOTS of problems ahead of you.