Dudes. I definitely have a hard time believing that there's a person out there who wouldn't like to coast downhill. Braking on a fixie scares the living daylights out of me, and it really doesn't seem sensible to pit your knees against however many descents you'll have for the rest of your life. I think fixies look rad, but that's kind of where it ends for me. You can achieve a very similar aesthetic with a single speed and save your knees. That's my take. I know there are all sorts of people who ride fixed, but the people who are doing it as a fashion statement really ruin it for everyone else. It just is an obvious disconnect from a bike being a useful transportation tool. Sometimes I think fixies are the kitted out Hondas of the bike world. A cheap product enhanced entirely for image, not practicality.
On the other hand...I think that fixies are ridiculously more fun and even safer in the hands of a competent rider in traffic. Yes, I said safer. With a front brake, that is. I was resistant to fixed riding when I first moved to Portland for pretty much the same reasons as you, Tim. I tried it and loved it. I really like the idea of being able to slow down substantially easier without having to touch a brake lever...just slow your feet down. Much easier to "flow" with traffic in downtown. I definitely agree with you on the knee, coasting and fashion statement arguments, however. In short, I want to build another nice urban-flavor fixie, but I'll ride my 1x8 with a smile on my face just the same.
I myself ride a '74 schwinn sprint, i ride single speed 16t with the alexrims dh16 unicog rims triple thick to beat potholes with the schwable marathon tires. moustache style bars. i ride single speed for a few reasons. I've had a few knee surgeries and i have a metal rod in my leg, and i dont believe i really want to fuck around. also i live in south dakota and our winters are really harsh and having all that derailer and gears would just get all mucked up.
Not that I do a whole lot of coasting (I have two speeds: full-speed and braking), but the idea of not being able to coast/focus on balance when I'm weaving between two lanes of traffic and dodging side mirrors seems disconnected from the bike to me.