If you have a VA loan and you want to simply lower your rate, did you know an appraisal is not required by the VA?  Some lenders require an appraisal as an in house rule, but the VA doesn't, so you should be able to find a lender who will let you lower your rate without any appraisal at all.

Pretty great deal for anybody with a VA loan that they got more than a year or two ago.