I've ridden a singlespeed Trek T1 as a daily commuter for a few years, ~16mi daily on the commute, add'tl miles for grocery, bar, etc. Even though I don't race, I opted for a stiffer bike to make the hills here a little easier on me.
I guess the ride can be a bit harsh, but I've learned my routes and avoid bumps as best I can. I have also ridden primarily aluminum bikes, so I don't have a great counterfactual.
Note that mine isn't stock, I'm not sure what the stock components are like if that's what you go for.