Interesting topic -
GMAT was a real pain when I started preparing - But the more I analyze and prepare, the more I feel it really serves the purpose.
Everyone says : If you study well , you will perform well in GMAT - Well that applies to may be the lucky 50% of the population. But why is the other 50% not performing well ?
Has anyone considered the psychological impact ? It is this aspect that GMAT helps to build indirectly.
Some of the positive effects from my experience -
1)
It helps me prioritize my work more effectively because I need to make time for studying - So I end up finding the easiest way to perform any task - aka Lazy man approach in DS

2)
It helps me handle pressure more effectively - The psychological buildup towards the test followed by the actual 4 hour grueling test - It exposes your limits and you discover that the only way to perform better is to practice this grueling exercise in a smart manner (I guess that is why disciplined people perform better in this test)
3)
It has helped me to apply my principle - Every mistake is a learning experienceThe list goes on...
I can summarize and say that GMAT is a good learning experience for me even though grueling at times.
Regarding top schools expecting high scores - They need to be top, so why should they NOT select the applicants with better scores? But the good thing is that "TOP" is relative for every school depending on the applicant background - So, Schools realize that they cannot solely rely on a GMAT score.
However, it is the way you approach that matters. If you consider the psychological aspects and use them to your advantage, you can develop a great EQ as well !!!
Believe me - In business or any work, IQ/verbal/number crunching skills do not matter after a certain point even if you are a pure Technical Analyst in an Investment Bank. It is the ability to handle pressure and failures that matters and helps you become a better person. This is from my experience.
Everyone is entitled to his/her own views. I have put my views.