Yes, however most computers are marketed using GHz numbers, not experienced performance (And in the cases where they are it's relative, like x times faster than before). It's hard to show a 17% slowdown to a store clerk.
Don't get me wrong, I'm all for being able to return a product that's 17% slower today than yesterday, I'm just saying it might be difficult since it's an issue that requires a degree of technical knowledge to understand which most store clerks don't have.