Recommendations for buying survey audiences

Have you used a vendor to purchase a survey audience?

If so, who?
Did they provide the incentive to the survey takers or did you?
Were you satisfied with how much you could "target" your desired
demographic?

Please reply offline and I'll compile a list of results. The only company
I'm familiar with is True Sample (offered through Zoomerang) but I'm sure
there must be others.

thanks!
Cindy

--
The Experience is the Product - http://www.cindyalvarez.com