IMHO single speed riding is a joy unto itself. I't's awesome on so many levels.

My Cross Check commuter was SS for years (42-16) A few years ago a crash messed up my knee and sadly SS just wasn't good for it in the long term. So I went to an IGH (Alfine 8) which is perfect as I can easily swap wheelsets any time if need be. Same chain length and horizontal drops. I always go SS in the spring for the first month after the studded tires come off, but then once my knee starts to complain I throw the IGH wheel back on. It's also nice if I get a flat at home or want to service the IGH I can just throw the SS wheel on and go.