Agreed with others - Love the design and it made a great first impression. Your explanation and walk through was very well done as well. I would maybe put a few cues as to which part can be hovered and more information will be presented.
After reading the blog post, I decided to hook up my little web app that I have been working on to use SendGrid. Although I had some trouble configuring it to work with Godaddy's Shared Hosting, I quickly took advantage of their email api. This is a pretty neat service and having 200 emails/day for me to use is great for testing.
Thanks for the insights and highlighting this service :)