The story about how the fourth bunker exploded (six years before the Chernobyl disaster!), about the Room that grants wishes, and about the stalker who takes people to this room for money is quite interesting, but still a bit tedious. Personally, I liked the movie; it has a deep meaning and is much better than modern AAA and YYY class projects. :)
P.S. Recently (April 4th), Tarkovsky (the director of "Stalker") would have turned 75.