My wife: the single speed rider BEFORE it was cool
I remember when I was young, having a single-speed bike meant you went and got the Wal-Mart cruiser $70 special. It was a joke, and the more speed you had, the cooler you were!
My wife (girlfriend at the time) had an old Schwinn 10-speed bike (no, she's not that old, she got it used). But she never switched gears! She put it in the gear she wanted, and stayed there! I always used to tease my wife about how she wasn't sophisticated enough on a bike to use all the gears. She was in-efficient. She didn't know better. She -gasp- wasn't cool!
Now times have changed! Single-speed bikes are cool! The less speeds, the better! I am infinitely jealous of my wife because I am building my own bike, and can't make it a single speed because I sometimes use it to tow my baby in her trailer, and don't want to die of exhaustion. I've also stripped the shifters and cables off my wife's schwinn, and she now I can ride next to her without hiding my face in shame! What great times we are in!
The moral of this story? My wife has taught me a valuable lesson: Do what makes YOU comfortable and what YOU want to do. If you only want one speed, use one speed. Don't bother worrying about what everyone else is doing. When I look back on our bike rides together, I was too busy worrying what gear was the :right" gear to be in while she was busy enjoying the scenery.
On a completely unrelated note, anyone have any good suggestions for how I can save a few extra grams of weight on my headset? Everyone says I need to get the lightest possible components for my bike, and 80 grams for a headset is ridiculous.