Bill,
What brand of devices do you use? I've never had a problem with #12 in Leviton or Eagle brand switches and recepts (15A).
Lighting I use a J box or two in the attic. The HR is to the J Box, and the Feeders "spider" out to each Sw box. The only thing in the Sw boxes are the feeder and the switched leg, or just a switch loop.
As far as #14... I've seen way too many old #14 wires in very poor shape. Corroded green on 1/3 of it's diameter, and very brittle from heat. I've seen #12 in the same location (and presumably, the same age) that was in convincingly better shape.
Warranties may only last a year, but I like my work to last a little longer than that.
