These are all valid points Dee. Lending Tree is strictly a referral service and banks and brokers pay Lending Tree for access to leads. In my humble opinion if a loan officer is good at what they do, then they should be able to build enough relationshps to generate their own leads. Same goes for any realtor, insurance agent, etc...
Keep in mind that no lender out there "magically" has access to money that is far cheaper than the next guy. Large institutions have a little more financial power, however, that advantage is often wiped out by the additional overhead they carry.
As a result, everyone is probably going to be pretty close to one another UNLESS they're pulling a fast one on you. And at the end of the day if you have problems or issues, it is not Lending Tree that is going to help you with them but rather the lender you work with anyway.
My advice is to ditch L-Tree and check with a couple local, reputable lenders and compare their options. Check with your banking institution and ask a couple friends or your realtor for a referral if you need to. This should ensure that you get good service, localized expertise, and a FAIR deal. Notice I didn't say the cheapest deal or the lowest rate. Keep in mind that you get what you pay for. I'd encourage you to consider how important the following factors are in making your decision: customer service, strentgth of the financial institution, and delivering on promises.
Best of luck!