I like that I can take a movie (after receiving it in the mail and watching it) to the store to immediately pick out a new one with my wife or my kids. It's instant gratification, and I don't have to wait for my best selection (usually).

Also, I get a free coupon every month for an additional in-store game or movie. My kids love this for games.

Lastly, you can now add games to your queue online, so it's like Gamefly + Movies.