I think this is an excellent way to acquire paying customers AND will give many potential users the option to see if they can build a decent subscribership without having to front the $250 or more that would be needed for ListBuilder.
We were so happy with the results and service, we doubled our mailing schedule!
I'm pretty stunned at how well your service works -- it's easily one of the most intuitive applications I've ever used. Most important, it seems to work! It took me only about an hour to get a newsletter through the test point. My highest compliments.