Just a wide variety. But, having these other activities helps keep you mentally active in a broader sense and allows you to be certainly a better team player. Click for RealPlayer video. Very important characteristic to be a whole person. Click for RealPlayer video.
Grades end up being very important.
I would like to say they are not important, but grades are one of the major tools that other people who don't know you use to evaluate your academic ability. So grades become important. What is truly important, however, is knowledge. If you learn a wide variety of things and learn your area of expertise well, hopefully that reflects in your grades. It does not always happen.