DanO,
At first I disliked the balance slider to blend KB sounds with arranger patterns too, but after a short while I found it to be better for the overal performance. If you raise the lead for a solo and never return it to a lower setting, you find yourself raising the acc to compensate, then another lead, another raise...till the volume creeps WAY up. The balance slider keeps things in proportion! I like it better this way.