A pre-finished box makes me scared of screwing it up. This is a good thing, because I was a lot more careful and only messed up the power jack hole.
It was fairly simple to transfer my guestimates from the cardboard mock-up to masking tape on the real box, with all the usual tweaking to get it to look right.
I drilled one of the jack holes to make sure I had the clearances for switch placement right... it would stink to screw that up. The jack holes are actually just a tiny bit tight at 3/8" (on the high quality jack), just had to wiggle the bit around slightly and then they popped in no problem.
This is what it looked like after drilling:
Step bits are awesome.