For horses of color i've always gone by the saying "god offered 'em spots or brains..."
I'm sure there are plenty of appys out there that are just awesome horses. I think that they are a bit harder to "get their number" than some of the other breeds, and that's why people find some to be so difficult.
Personally? I don't like the excess pink skin found on many appys, nor the tendency for many to have small/pig eyes (i also go by the saying for all horses that only the crazy or dumb ones have small eyes; the bigger the eye, the bigger the brain!) I'm not a huge fan of loud coloring, either, so if I were in the market for another horse, I probably would not look at an appy. I do love their little broomstick tails and scraggly manes though - - that I think looks cute :)