The problem with effort is that as you progress towards the top levels of any given skill set, you have to work exponentially harder to see incremental improvements.
Imagine a novice guitar player. It takes him a month or two to learn a few open chords and soon he is strumming his way through a selection of campfire classics. This is enough for many people to label him a "guitarist." The next level of musicianship requires him to learn moveable chords, pentatonic scales, and a few hammer-ons well enough to work them seamlessly into songs. This requires a bit more effort. But within a year or so, 90% of people will nod their heads and say, "Hey, you're pretty good at guitar." To get to the next level, he has to learn some theory, to study major and minor scales and their relationship to chords, to spend hours with a metronome, and to integrate this knowledge so fully it becomes instinctual. It may take years. Yet to the untrained ear, it doesn't sound terribly different from what our imaginary guitarist was playing before. He soldiers on and spends a decade mastering sweep picking, tapping, and palm muting. But he finds these techniques are only usable for a few seconds of any given song, and most listeners don't recognize them anyway, lumping them all into the category of "Playing Guitar Real Fast." A virtuoso - Vai, Gilbert, Buckethead, Bumblefoot - has invested tens of thousands of hours developing skills so refined that only a tiny fraction of human beings can possibly appreciate them.
In P. H. Mullen Jr.'s Gold in the Water, swimmer Sergey Mariniuk is puzzled by the same phenomenon. He finds he only needs four hours of training every week to achieve speeds that guarantee him a slot on his country's Olympic team, but he'd need upwards of 20 hours of weekly training to knock another three seconds off his time. A 500% increase in effort to achieve an almost immeasurable increase in speed. He decides the added struggle is not worth it. After all, what's the difference between seventh and sixth place?
It's not that effort is bad. It's that it is most efficiently applied to learning new skills, not refining existing ones. This is the exact opposite of the way most of us lead our lives. We jump and sweat, trying to reach the next plateau, never realizing that amazing things are easily within our grasp if we're willing to walk in an entirely new direction.
[Ed. - I am not sure I agree with my own post here. But it is an idea that has been rattling around in my head for awhile and I enjoyed writing it. I think that I think that excellence has some intrinsic value. And while effort may not be efficient, it is still worthwhile.]