Installed the HD add-a-leaf in my Medium Duty Old Man Emu leaf pack. So far, I love the slightly stiffer ride (I don't care what all the reviews say, it DOES NOT ride like a dump truck), and I was able to drop down to the middle hole on my PRG shackles and still gained about 3/4 of an inch of height in the rear, which now has my truck sitting PERFECT (I had a slight sag / bro-dozer look going on, which only got worse when I was loaded down for a trip).
I took GlamisDude's advice and installed some shims within the pack to cut down on noise (note: I was not experiencing any squeaking or noises, but from what I've read, I figured it was only a matter of time. The leafs have been installed since I did my axle swap about 8 months ago). He's got some great advice in a thread over on TNX. Unfortunately, I was not able to drill into the AAL themselves (burned through 6 drill bits trying), so I don't have the shims installed everywhere in the pack. I'm hopeful that they stay quiet. I did notice that my OME bushings are already in pretty bad shape (another widely-commented issue within all of the reviews). Had I thought about it ahead of time, I would have had a new set of bushings ready to install today, but I guess I'll just run these ones until they're too sloppy to tolerate.