The general idea behind Amdahl's law is that improving one thing may cause other things to be the limiting factor. The discovery that we could prevent scurvy just by getting enough vitamin C was great, and it all-but-eliminated scurvy-related problems from our lives, but it doesn't do much for other problems, like hurricanes, alcoholism, and monkey gangs. I personally would love to have a magic bullet that would prevent me from ever stubbing my toe. It wouldn't solve all our problems, but I have yet to find anybody, even masochists who get off on severe pain, who wants to continue getting stubbed toes. Amdahl's law isn't something you can get away from, but it's something you can work with.

Gustafson's law, which you linked to, isn't a rebuttal to Amdahl's law -- more like an addendum. If you have a really good solution to one problem, you can sometimes recast other problems in terms of it. If we ever get our shit together and start churning out Liquid Fluoride Thorium Reactors (PDF) in bulk, then it would do more than solve our electricity woes. We could take some other problems -- not enough fertilizer, shortages of fresh water, oil supply problems -- and recast those in a form that we can solve with LFTRs. The high temperatures from LFTRs can make ammonia, synthetic fuels for internal combustion engines, and fresh water. One solution becomes many solutions.