A pre-approval may help you negotiate a better price and/or terms with the seller, because they know that the buyer is serious enough to have answered the hard questions with a lender. Often having a pre-approval at the ready can give you a leg-up if you are up against another buyer who did not come to the table so well prepared.
The better course of action if you are a serious buyer is to utilize the Pre-Approval Letter. This can only be secured through a lender. Given the buyers market we have now, the pre-approval letter is still all-important. Everyone has heard of the high foreclosure rates, short sales and, frankly, all of us are suffering at the gas pump. This makes a pre-approval letter an absolute must in these times.