http://flyanglersonline.com/features/bamboo/part29.php

Rod/Reel Balance is not important for casting but it is for fishing. I believe this is what johnstoeckel is saying. You want the rod to "naturally" assume the position at which you normally fish, when you have the amount the of line out that is your normal cast.

If you tight line nymph with the rod tip up, you want the rod to to assume that position when you have the average amount of line out of the guides. If you most often fish streamers with the rod tip down at the water level, then you want the rod/reel to balance tip down.

As Jesse says, you can adjust the grip point after the cast to get the rod to balance more tip up or down.