I invite you to read reviews that actually measure efficiency. It isn't marketing crapola, it is fact. Hell, even read the 80 PLUS specifications.
http://en.wikipedia.org/wiki/80_PLUS#Efficiency_level_certifications
Any gaming rig is going to look at a ballpark of 500-550w for a solid single GPU and... what, 650-750w for CFX/SLI (maybe more if you use three GPUs in one CFX/SLI setup)? I don't think I'd want to have to spend the money on a 1200w+ quality PSU just to get the supposed benefits of the "50% = maximum efficiency" rumor.
It's just one benefit that I think is overshadowed by the fact that I'd save a lot of money if I didn't shell out hundreds of dollars for wattage I'll never use and never see any practical use out of.
If there is solid evidence (aside from Wikipedia and what the power supply marketing teams claim) to support this notion, I will happily eat a sock.

















