I agree with both what RB and what Allan said: Creeds are useful but we can't overemphasize them and they have no authority as the Bible does.
However, since creeds came about as responses to attacks on the faith, I do find them quite useful in clarifying beliefs. For example, I have been surprised at the number of believers who do not seem to think being against the Trinity is a problem. I kid you not! (When I have time, I might start a thread on this).
When I come across this, I will often find the Athanasian Creed and send it to them to show how imporant the Trinity is, and explain the Sabellian heresy.
Example: T D Jakes denies the Trinity but he's so popular. When I've told some believers this, their response is sometimes, "Well, does it matter that much if he denies the Trinity?" I think there is a de-emphasis on doctrine going on in the church that is very dangerous.
I better get off my soapbox -- I can feel a speech coming on!