Links: TVTropes, Wikipedia, IMDB (8.3).
Each time I watch this film, I find myself torn between loving it and mildly disliking it. On one hand: the concept is great, Ridley Scott's visuals are great, Vangelis's score is great, and Rutger Hauer (!) completely steals the show and delivers a knock-down performance. On the other hand: Harrison Ford's Deckard is a generic cardboard cutout (no fault of Ford's, just lazy writing), Sean Young seems to have been told that her character is made of wood, and the borrowings from Film Noir result in a yawn-worthy, slow-moving 2 hour film that's about half an hour too long. (Cutting Deckard's off-the-job character "development" could recover most of that and the movie wouldn't be hurt by its removal. Really, we know the genre, of course he's an alcoholic hard-boiled detective who can't resist a bird with a broken wing.) The opening visuals are infamously gorgeous, and the last half hour is superb, but... be ready to be bored in between those two. That said, it has its reputation as a sci-fi film masterpiece for a reason. Score: 4 stars out of 4.
Note: Avoid the 1982 theatrical release at all costs, with its infamously bad voiceover by Harrison Ford, because it's noticeably inferior to later versions of the film. In contrast, there isn't much of a difference between the 1992 Director's Cut vs the 2007 Final Cut: added violence, a few audio improvements and dialogue patch-ups, and an improved unicorn dream sequence. Watch the Final Cut over the Director's Cut if you have a choice between them, but you're not missing much if you've only seen the 1992 version.