I think the weakest thing about Alien Resurrection is Winona Ryder, i don't particularly like her as an actress, but i thought she was downright terrible in AR.
As an Alien fan though, i still like AR, but it is definitely the weakest of the four films, and it proves that the sun doesn't shine out of scriptwriter Joss Whedon's arse like most Sci-Fi fans think it does...I seriously don't get what people see in Firefly/Serenity, it was rightfully cancelled imo (i'm sure that will upset a few people, but i hope you agree that i'm entitled to my opinion).
Anyone who didn't like Alien 3 will be pleasantly surprised by the Special Edition though, the extra 30 minutes really adRAB to the story and characters.