Market Leader depends on 'outbound' marketing. This is NOT where you want to spend your precious marketing money.
Finally, using resources like Market Leader is like having another job. You are brow beat into responding to all inquiries within 1.6 microseconds. Yep, a full time job chasing VAPORS!
Be aware, there is not reason to believe their integrity is better than that of the mother ship.
There is a way, a key indicator, with Market Leader, that allows you to identify the serious buyers and sellers from the trolls. Using this indicator, from my personal stats, identifies who will make a real estate decision in the next 12 months. (Actual data: 90%) Now that is the lead worth chasing.
In summary, it bad and ugly if you dance the jig prescribed by the program.
Good if you apply your personal experience and actually bore into the data to separate the unicorns from the realities of real estate.
Disclosure: I use Market Leader landing pages and feed them with my own adwords. I DO NOT BUY LEADS...........anymore.