Just a heads up : not sure if anyone know about it, but Linear Technology let you download "SwitcherCAD" that is not just to simulate their parts; it allows you to simulate pretty much anything; from a power supply to PWM, transistors and whatever you like...
It can plot graphs of voltage/power at various points in the circuit just by clicking.
Awesome ! :D
Oh, extra brownie points : it runs great in wine under linux (debian)