I've been using DesignQuote on and off for a little over 6 months. I purchase leads for my business: coactivated.com when I don't have the time to develop my own campaign for fresh leads.
It's difficult to lay blame on the staff at DesignQuote.net for the nature of pitching to people who are not investing anything to request a quote. Even if you gather leads on your own, you're going to get that more often than you'd want.
So far my experience with them has included a few bad eggs and a few good ones too. I feel like they're doing their best to weed out the bad eggs and I can see why they're unwilling to offer refunds, though I think there should be more of a commitment on the client's end.
This is a "participate at your own risk" service, I would suggest that anyone looks to find Design Quote leads first be sure they have a solid, tested, proposal process. In other words, don't purchase from them if your process includes spending hours on a proposal before you speak directly to the client.