I've read the William Gibson draft and thought it was terrible. There were a couple good ideas in there but overall I thought it was weak. I've found that Alien 3 grows on you. True, the special effects look a little odd, but frankly, I think they worked better than some of the CGI you see today, twenty years later. It has a darker atmosphere than the first two movies and I think Fincher did a great job of keeping things fresh. I think a lot of monster movies start with a good first installment, add some cool stuff in the sequel and then ruin it in the third by just adding some weird crap, like the creatures in Tremors 3 who could fly with exploding farts. I like that they were able to create and maintain tension with just a single monster with only a few slight changes to it's design.