Well, I got my copy of Castle Greyhawk. It's every bit as bad as I recalled and then some. I mean, there's one level that features a B-52 bomber and offers a 5-10 thousand XP bonus to the first player who mentions that B-52 did not fly in WWII. I kept thinking that the art looked very Paranoia-esque, which made sense when I finally looked and saw that the art was done by Jim Halloway. How Paranoia-esque was it? There was a drawing of a pair of smoking boots where an adventurer once stood.
It's utter rubbish, but it's nice to have a copy of this peice of rubbish from my childhood.