I've had about a 50% success rate in the WTB. Haven't asked for anything major, yet, but I plan to in the future. From what I've seen, if somebody is asking for some higher dollar books, they seem to get responses quicker. Understandable. But those that want the obscure books may not be reaching those sellers that have had their fill of the WTB section.
I'll answer all messages and will sometimes buy multiples of the book if I have 2 courteous sellers and the prices are fair. Not extremely high dollar, but fair prices with fair shipping.
As a new collector the WTB will be a valuable forum. I've even made a purchase of a book that was turned down by another WTB thread.
I would hate to think that somebody would waste time on me. If they are going to message me, I'll message back. Simple.