I have used quite a few different services of your kind, and I think yours provides the most value for the money of any I've seen. Great tool!
Your customer service is 100X better than the other e-mail providers.
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.