Smaller states would still matter because they are winner takes all, but larger states would become more interesting, because all of a sudden Texas isn't just Republic, nor California or New York just Democrat. Florida would probably be less important because it's so evenly split, and Ohio would fade slightly. In other words, it would even out campaigns and force them to be national, without the terrifying thought of a nationwide recount or further erosion of the principle of a two-tiered (Federal) system of government.

That would make even the smaller states more competitive and certainly would make individual votes count more within all 50 states.