Bringing this thread back-
I didn't plan to buy a bike with disc brakes but when I replaced my stolen Ruby I ended up with them. I rarely ride in the rain in Tucson, although I do think they will be nice to have for coming down Mt. Lemmon.

I didn't thing there was that much of a difference until I got off my road bike and got on to my Surly LHT to get groceries. WOW- what a huge difference! Maybe they were already less responsive, but it took noticeably more effort to stop on the Surly (with rim brakes). And that was riding the Surly unloaded!

I'm sure I'd appreciate them even more if I was riding in wet weather.