My normal commute route is quite flat, and my primary commuter bike is a single-speed. I like to coast, so I don't run fixed.

If I have after-work activities that take me further east, then I have a few hills I have to deal with. Very ride-able hills, but enough of them in a week and my knees feel it.

If I need to haul anything heavy, I'm riding a geared bike. I made the mistake once of hauling 80lbs of pet supplies in a trailer towed behind the single-speed. Even tiny hills became a problem.

I did ride a 100K populaire with a group of strong riders earlier this year. I was the only bozo on a single-speed. It was a moderately hilly route. I did fall behind, but still made the time cutoff.

My SS is geared about 65 gear-inches. I completely understand the wind being an issue. However, I don't live next to a big lake.