Well it's a product that I use every day and I'm always eager to try new stuff if I see it could be cool. I was really interessed by the article and headed to the website to see what it offered, and I felt it wasn't a plugin that would suit me. There is always place for improvement, even if I think Gmail is great as it is right now.
Sometimes, you're so used to a certain interface that you don't even know you can improve it until someone comes at you with something new and say "look, here's a new feature we thought you'd like : " and you go "yeah! why didn't I think of this first?".
Sounds like you're not even a member of their potential user base if you're already happy with the Gmail interface.