I did a small test with their e-mail submits.. conversions weren't what I expected, so you might be right (once again,
small test

)
Someone needs to test these on a larger scale with a bit of traffic volume, then we'll know for sure. I don't believe they convert if the visitor simply enters their email on the first page, but the advertiser requires them to at least (attempt) to fill out the next page with their personal information.. or they're just scrubbing leads for some reason.
I'm sure it's all depends on the offer, though. There's probably some nice converting ones out there, just not enough data yet to show others that they do convert well.
Best,
- Metra