can you mix wire gauge?
Even though it's harder to work with, you did a good thing running 12 AWG. More options, better ability to upgrade in the future.
Just last week I started a systematic walk-through of the wiring in the house I just bought (1916 Queen Anne). I've already pulled new wire through 85% of it, and this time I started pigtailing with 14G on circuits that I know will never be greater than 15A (lighting, etc.). Now I'm tempted to change my plan and revert to 12G pigtailing just to be absolutely consistent.
I've read that careful wire placement (folding and pushing) with linesman's pliers is a common technique to get the wires stored properly, and this seems to work well. Still, when you are wiring a fixture you can still be stuck coaxing the spliced wires back up into the box and around the center mounting strap.
Personally, I'm interested in the common practice in the field. Is it better to keep a 12G run "pure" the whole way? Is pigtailing with 14G (to 12G) on a 15A circuit a common technique? Any comments on the pros/cons would help.