I really liked 10 Jackpointers. Gives the characters a bit more punch when they talk in the other books to my mind. I don't feel bad buying that one.
Oh, It was awesome. I used the Interpol style reports that the Dawkins Group did as templates for creating files for my PCs and let them discover exactly what the Man knows...and watched the paranoia mount.
I would really like to see additional jackpointers materials, and maybe materials for characters from the older editions along the same vein.