If you're sending confidential information from Gmail the G is reading and storing your email. I would be more worried by that than some (highly unlikely) man in the middle attack. Google scan everything, store it forever, pass anything 'suspicious' to the FBI, and use everything you type to profile and then advertise at you.
That's way more frightening than some snooper down the line. Which is unlikely given that the route your message takes through the internet is essentially random, and even to cover some of the possible routes the attacker would have to compromise either the large bulk servers at the ISP at one or other end of the route, or else the major servers on the internet backbone. How likely is that?
No, I'd be more worried by what you're letting Google see.