Thanks.
Yes a little in smps applications, and a fair bit in motor control.
I built a nixie clock, ht for the tubes came from a switching supply controlled from the pic16f628a, it was a simple feedbackless loop, brightness was adjustable in software, all the pic did though was generate a variable pulse width, no feedback.
This has been done using something like a pic16f88 using an analogue channel as feedback, this can get real ugly with the control algorithm when you start thinking about things like compensation.
Do you want to build a smps using just a pic and discretes, or do you want to be able to control a smps chip using a micro, the latter is a more practical approach unless your mass producing something and really need to cut costs.