Yessir. I did extensive small scale testing before I had the funds to build my entire rig. I had concerns about the same thing, and also how the duty cycle of the PWM might not work in conjunction with the 60hz cycle of AC current. To my surprise, with an inductive ammeter and a DVOM set to voltage, I found that the above linked PWM could give you a very smooth, linear voltage supply from 0-100% of your available household supply. If you looked at the line with a lab scope, I'm sure there are slight variations, but for our purposes, it works.
Yes, on a very micro scale you are quite right Bobby but that amperage spike is probably measured in nanoseconds and doesn't have the time required to trip a breaker, heat up a wire, or even register on either of my meters. I have two of those PWMs wired in parallel to the PIDs on my rig. This allows for manual override of the PIDs and also, if I choose to transport my rig say out to my patio, I now have the option of using my 20A 240V air conditioning circuit. (Instead of my 30a service I use inside the apartment) I cannot let the PID control the 5500W element, because the PID cycles too slowly and will trip the breaker every time, but I can use my PWM and keep the applied amperage under 75%.
I wish I had shot some footage with the meters in place, but here is something I threw on the interwebs showing my small scale testing.
Video Link: http://www.youtube.com/watch?v=ePc3zpyAeoY&feature=plcp
Just a heads up to anyone else reading this though, this most likely will not work on anything with an AC motor! You will still want to use a ceiling fan controller or something if you are stirring wort or grinding grain due to that whole cycle thing I mentioned earlier ;-)