I've run BB7s for years on various bikes, I'm not really a fan. They work well, but setup and maintenance is a bit of extra hassle. I don't like brake rub and a lot of things have to come together to avoid it easily and completely. They aren't more powerful than the caliper brakes I have on my other brakes, though more consistent in all conditions. They are a bit harder to modulate, but that's a minor thing. I keep them because I don't like buying rims every spring, but even with that hassle my next bike will almost certainly be caliper. Unless I get really fancy and go hydro, but it's expensive for a winter trainer.