Has anyone ever experienced frost on your mig regulator's? I'm using c25 and had my flow rate set at around 13 cfh and when I finished I had a slight bit of frost on my regs.

I believe this just happens as a result of the CO2 content. If you look at different regulators/flowmeters, you'll notice that most mfg's offer heated options for CO2 regulators/flowmeters to solve freezing issues. When using it for welding, especially with 25% or lower CO2 content, it shouldn't cause any real problems as far as I know. I've occasionally seen 100% C02 used for GMAW-S w/ no mechanism ever in place to combat this effect, so it doesn't seem like much of a concern at the pressure & flow rates used for welding.