I didn't like this deck for a long time because of its ambiguity. It seems the question on everyone's mind (mine as well) when they think of Crowley - was he or wasn't he? (a Satanist, that is). Crowley asked himself the same question, but never did answer it definitively as far as I know.
Now I find the ambiguity stimulating. The deck contains elements of both dark and light, but they are not clearly defined. You're always left guessing, which on the one hand can be maddening, but on the other it's never boring.
I haven't used it for readings yet, but I'm looking forward to the day I do. I suspect it should be quite interesting.
There are many different versions of this deck. I find the AG Muller versions to be the best, imo. The card stock seems of a better quality, the colors are richer, and the images crisper. The AG Muller's I've seen are usually in a US Games box, and there's a sticker on the shrink wrap that says AG Muller. I don't know if all the US Games versions are AG Muller or not; all the newer ones I've seen are.
-fof