There are ways to critique something without calling it "really useless".
Sounds like you're not even a member of their potential user base if you're already happy with the Gmail interface.
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?".
Words that needed to be said, thank you for doing so.
@Khao: Tone is critical when giving sincere opinion. Moreover, tone is hard to convey through text. I believe you should choose your words more carefully. Your post (to me) is somewhat fussy.