I'm running a 12f617 at 24mhz and a 16f627 at 27mhz right now, simple programs that flash an led, but use loops of math problems to create pauses, to put more load on the chip. So far they have been running for a few hours without a problem, I will be ordering a 30mhz crystal in a few days, hopefully it'll work. How far have you guys pushed your PIC's? and what problems can I expect if I keep pushing them? I will only be overclocking for personal use FYI.