Since you mentioned "ethics," consider this. What if your lender said:"I had locked my refi on 4-26, can I get out of it now? It seems as if rates have gone up enough to make a difference?". If you would be comfortable with that scenario, then I say you are fine to break your lock and look elsewhere.

You have several options: Most lenders have some kind of float down with their locks if the rates are 1/4% or better, but it might depend if it is a broker or direct lender. Ask your loan officer. You could start with a second lender , but if an appraisal has been done you probably will not be able to transfer it. (unless FHA) . I would suggest you give your current lender first crack and then go from there.

From an ethical view , you should close at the price you locked , the lender should deliver the rate you locked , even if they go up and you should close at the rate you locked even if they went down. It's pretty straight forward.

My recommendation is to work with your current lender and see if they can offer you a lower rate like mentioned above by mfcfed. Some lenders have the float down. You have the option to walk away as a borrower but lenders do not like to see that of course. These days lenders will only lock once out of underwriting that I am aware of. My chartered bank I work for can lock a rate immediately upon taking an application and then work with the borrower on the market should rates go back down. I just had the same scenario and borrower got the lower rate and now my bank is giving my client a credit. Rate was locked at 4.875 back on April 20th or so..rates have declined and my pricing dept has offered my borrower 4.75 no pts and a $480 credit back...so it's about negotiation in my thoughts. Should you need references, let me know.