We own a 2012 SE manual, and drive it @ 80 mph every chance we get. Yes, it's spinning at 3,500 rpm, but the engine seems to love it. No whine, no real noise issues, and great mpg.
We've averaged 35 mpg over the first 9,500 miles, according to the onboard computer. The last 500, with winter gas and more local driving than usual, has registered 32.5. Even if those readings are 10% optimistic, we're ahead of the game.
Would a six-speed manual be even better? No doubt. But we've been perfectly happy with the five-speed. So will you.