Well, I'll touch on the subject of QA with Ork stuff, to tie it into the original topic.
Aside from the typos that show up in places in the Ork codex for the Kindle (i.e. there's a pair of capital W's in the middle of a sentence for no reason), a more annoying problem has been finding errors with the instructions for various kits. I just assembled a new set of MegaNobz, a Blitza Bomma, and a pair of Deff Dreads, and each set of instructions had somewhere that a part number was wrong. One case was as "harmless" as getting the numbers of a pair of pieces that'd be attached to each other wrong; another had a typo in the first digit of a part number; yet another had the wrong number entirely for a part and I had to look really hard at the part on the sprue and compare it to the illustrations to make sure it was the right part. If I wasn't so experienced at assembling kits, I might have run into serious issues there. That's just not cool.
And any amount of playtesting at all would have told them Knights needed to cost more and shouldn't be an entire army, and that Invisibility shouldn't have gotten into the rulebook in that format.