Pain becomes different too. The little pebble that is nothing at 41F / 5 C can become painful at 23 F /-5 C. You're also more likely to injure yourself, stub your toe, or land badly, when your feet start to numb up a bit, so you got to be extra vigilante about good form, especially at faster paces...
I noticed this too last year. Along with winter came tons of little chips on the road, not sure if they came along with the salt truck or what. These little chips wouldn't have been a big deal in summer I don't think, but they made it impossible for me to run without pain. I couldnt handle much cold either, just in the 30's I'd be numb, and even trying to pay close attention to picking my feet up and landing softly and I would have burning soles for a few hours after my runs. I havent done much cold weather running yet myself this year, so the jury is still out on what I can handle now after a full year.