AR1215's have saved my a** and the show a couple of times...more than enough to pay for themselves. Of course, they are not "power conditioners", but pretty fair line voltage regulators.
I don't know if it saved my posterior, but it is a bit of piece of mind. Nice when the genny line hits 100v at FOH. As far as smoothing out the crap power from an construction genny, that's an entirely different kettle of fish. At least the voltage is there - for better or worse... Running that through the double conversion UPS after the 1215 would be a bit sweeter.
Low voltage - another thing power conditioners won't help at all with. And by the way, the Crown XTI amps DO NOT LIKE low voltage (<=100 volts) They tend to clip prematurely and sound dreadful when they do.
[size=78%] [/size]frank