I picked up the WoW boxset at a gaming auction during a convention back in 1991 or so. Futureworld was cool, but I really liked the simpler version of Superworld (compared to the Superworld boxed set which felt like it complicated things too much) along with several pages of designer notes from Different Worlds #23.
The WoW boxed set was so very close to being one of, if not the very first, universal RPG on the market. I would have loved to have seen a second WoW boxed set with Post Apocalypse/Wild West/Pirate settings.