"I just wanted to thank you for the advice you gave me on your Query Shark blog. I struggled to write an effective query letter, and it wasn't until I applied your advice and wrote the revised version posted on your site that I started getting legitimate hits. And, I'm happy to say, I recently signed with an agent who I'm very excited about. Hopefully, we will have success in finding a publisher - we'll see - but I wanted to say thank you for all of your help."
Well! That's the kind of news that makes even the shark smile!