Tallhair . . . Yes, I've installed one in my house, and I went even further and added "radiant barrier" to the bottom of all the roof rafters. So, the eaves have vents in them to allow cool air in, and the ridge has a vent, to allow the hot air out. The radiant barrier keeps a majority of the heat in the 3 1/2 inch space between the roof decking and the radiant barrier on the bottom of the roof rafters. In addition, I've added an exhaust fan in one of the eaves so that when the heat hits a specified temperature, it turns on and evacuates the hot air out - pulling "cooler" air in the other two vents. Cooler is a relative term when it's 100 degrees outside.
Had my AC man over to help with the heat pump, and he went up in my attic on a day that was 90 degrees outside, to show him how well it worked - he could not believe how "nice" it was in the attic ! ! ! He swore he was going to do the same thing to his attic. As for my electric bill, the previous August the bill was $120, and the year after I added the radiant barrier, the bill was between $80-90. Make's it much nicer in the house too - although I know I need more attic insulation and just have not got around to doing it - I HATE WORKING WITH INSULATION ! !
If you'd like to know more, I can post some pictures . . . or PM me for my number, you're more than welcome to call anytime.
Getting the heat out of the attic ( or keeping it out of there ) will make a world of difference in the living area below it.