I had a SS (Langster), I wanted to use it for commuting and general noodling around town, but I just couldn't be happy with the single gear ratio. I "auditioned" the idea of a singlespeed by riding my road bike for a week with the same combo that the Langster had, and I figured it would be doable-yet-difficult depending on the hill. I considered changing the gearing to something more hill-friendly, but then I'd end up twirling the crank pretty quickly at only moderate speeds on the flats.

I ended up selling it, but only partly because I wanted to stick with multispeed bikes; there were other reasons that had nothing to do with it being a singlespeed.