it's pretty cold out these days and yesterday at zero degrees my suspension fork didn't work, it was rather ridgid, extremely ridgid. I've known this for years, but I've really noticed a lot more ridgid forks being used in the cold weather. I don't think there is a bicycle suspension that will work properly below 10 degrees. Front suspension is the ultimate in the summer. But in the snow I think ridgid forks make more sense. in fact a ridgid singlespeed would probably be the ultimate winter bike (at least riding through the snow) I can't lock my 27 speed mountain bike to anything, because it would get stripped down with allen wrenches, but you can build a cool ridgid frame that would be easier to lock and less attractive to theives. As far as a single speed goes you dont need that many gear changes riding in snowy conditions, and you might get stuck in one gear anyway, if your derailler becomes "caked" with ice. I've seen singlespeeds do the trails also (but they gotta be limited on climbing hills) nothing beats a properly built suspension bike, unless you ride in the snow. Ridgid frames make an excellent second choice.