I actually initially liked the lumbar pad. But last week with the peragrine in day pack mode I hunted 2 days with the lumbar pad on then 2 days with it off. I was pleasantly surprised that it actually felt better off. But then again that is with Probably 12-15 pounds of weight in daypack mode
I ditched my lumbar altogether -- I used it because I wanted the pack a bit further away from my butt. FWIW, 1 inch or less extra torso length adjustment (i.e. I added 3/4 of a inch, or something), dialled in the fit and I do not miss the LP at any weight.