Having a person coming out of Google would be great not only because you know they have some skills, but that they are completely committed and determined to get it done. What a great coworker they would be!.
As comfortable as Google is you're right in acknowledging that there are more ambitious challenges to be had.
Good luck -- enjoy the ride.
"Fortune and love favor the brave" -- Ovid
So what is Xobni about? "Making email smarter", as they write on their homepage, is not a very profound description.