I have a bunch of friends that subscribe to it, and our GIS Coordinator swears by it - it's a great deal if you watch a lot of movies, since you can keep them as long as you want (i.e. no late charges) and you can set your queue to be quite lengthy.
They also have a lot of obscure things that Blockbuster wouldn't necessarily carry.
I had it, but cancelled after 3 months. You can only take out 3 movies at a time unless you get the premium memberships. It worked out that if you watched the movies on the weekend and returned them in the mail on Monday you wouldn't get your next 3 movies until the following week. So you went a weekend without movies.
I wasn't too happy with it. I ended up getting like maybe 9 movies a month, and they are shipped and returned in just paper envelopes, no DVD case. So half the time the movie was too scratched to watch.
I wouldn't recommend unless you really want the obscure stuff, because the New Releases are usually backordered.