One power conditioning design I did see that made a lot of sense to me was a large capacitor on the input and positive was connected to automotive power "in case the starter tries to drain the capacitor"
For some reason I have a real hard time putting a voltage regulator (zener) on a voltage regulator, but a large capacitor should smooth things out and reduce/eliminate brownouts, which the atmega definately doesn't like, especially with a diode there. Thoughts? Is that a reasonable compromise between DIY "good enough" and "clean room" mentality and complexity? Which would also add a fair degree of reliability to the power supply at the same time?
edit: updated schematic/board in post 9. Also note futurelec sems to have very reasonable prices for no-frills prototype boards, especially single sided. Any others? I have zero experience here.
Also what about buttons? I wind up custom fabbing them to keep the front profile to a minimum, but what are the options there? Also I like pressing down on them since it doen't test the strength of my velcro so much.