I refinanced my loan through LendingTree last year. If you do it, be prepared to be inundated with emails from a bunch of different lenders, and be prepared for them to call you and bother you for a few weeks. However, it really is the best way to get the lowest rate on a mortgage. I shopped around online and with my own bank, and one of LendingTree's offers ended up being the best priced deal. They only get a 3 from me though, because they didn't have a ton of offers for me because they don't have a lot of lenders who are willing to lend to co-op owners.

I have refinance my home through LendingTree and received a good rate. The experience overall was pretty mediocre, particularly online where the offer presentation was weak. Most of the experience felt really traditional after the online form is filled out. Loan officers call you and compel you to lock in an interest rate. You can play the loan officers off each other and get a better rate.
The online experience is tedious. The form is long and the email barrage after the form submit is intense. Still, if you can endure, you can negotiate a rate that is better than the bankrate average.