I got my last loan through LendingTree. I submitted a form and only received two offers which surprised me.

One of the offers was not competitive. I ended up closing with the other offer. Here are my observations on the process
1) Way too many emails to me from LendingTree
2) The loan agents that called me from the lenders were great. They knew the terms, talked favorably about LT
3) When I mentioned that I was talking to the other bank, the bank I ended up closing with gave me a better deal. So the competition was real
4) No problem working from a lender that was far away. The lender that I close with was in Kansas City, and I live in WY.
5) The realtor I was using wasn't too keen on me using an outside company. But, she agreed to it and we had no problem at the closing table at the end.
GOOD: Fast, easy service, LendingTree is a trusted name, rates were really good (with one bank), loan agents very helpful
BAD: Too many follow ups between the agents and LendingTree emails, only two offers (they say you should get four), and the tools to manage the offer online were weak at best.
Bottom line, it's a free service so give it a shot. But, make sure to compare those rates to what you get on bankrate.