The initial deal is great. We don't buy every month for various reasons. Occasionally DMC has sent us the movie regardless of opting out, but not to the point where it's that annoying. I do wish they'd stop it though. Buying new movies is a little frustrating because they're almost always on sale cheaper at a box store, but... lately DMC is more valuable because of 2 movie combo deals. And you certainly can't beat the convenience.
I also like the Blu Ray shorts collections that I'd probably never convince myself to buy without DMC. We have the Pixar one, Halloween one, and Mickey's Once & Twice Upon a Christmas.
Also, DMC is amazing for getting Disney Movie Rewards points!