I've found most THW games to be fairly simple, but I will note that they have some -very- unusual mechanisms. Some folks pick them up right away - others might take a game or two to familiarize themselves. Most gamers I know either love THW games or loathe them. Some of them on both sides happen to be in my gaming group;)
I will say that "All Things Horror" seems a misnomer to me, since it's predominantly WWW2 based, and is specifically geared toward that era. There was some amusing chatter about that over at TMP.
-Doc