How many banks competing for your mortgage?

[Stone Teran]

In the past, I've talked to a few banks and I went "through the process" with 1 bank that had the best numbers up front.  The refinance I am pursuing now is much larger so even a .25% difference in rate is huge.  Is it OK to "go through the process" with 3 banks and have them compete against each other on rate?  All 3 banks are in the same range of rates but I've learned they can shave a little off the rate if they really want your business.  I plan to have the primary bank get the appraisal and have the other 2 use that same appraisal.  I really don't want to waste their time but I do want the best rate.