I have limited experience with AP, but from my results it looks like it is going to be the powder I use from now on.
I have a 32 caliber that I was trying out different powders in. The AP gave at least as good of groups as pyrodex or 777. The bore has to be clean of any lubes and you can't use any. I swab the bore with alcohol before doing any shooting. I shoot a charge or two without a ball then load the first ball with spit lube. All the next shots are made with the patch cut at the muzzle and loaded dry. The patched ball is easy to load dry. I have shot 30-40 shots without any cleaning between shots and no change in accuracy. 32s foul easily and I can't shoot without cleaning with the other powders. End of day cleanup was easy.
I tried AP in a new 1861 36 caliber Colt revolver. I cleaned the cylider and bore with alcohol and fired a cylinder without a ball. I noticed while loading that the AP powder compresses much more than pyrodex or 777. Again I didn't use any lube. I got better grouping with the AP than with the other powders I have used. I was able to shoot the gun quite a bit without any binding or need to clean. I have a Remington 1858 in 36 caliber that I can only shoot a few cylinders with pyrodex before it binds up - I need to try the AP in it.
I tried shooting AP in a 50 caliber, but I was using a lube and cleanup was a pain. I have about 10 lbs of Pyrodex, 777, and Clear Shot that I need to shoot up so won't be using the AP in the big bores for awhile.
I can't comment on the big bores, but for small bores the AP is great stuff.