Yes, very easy; you get an email notification, it takes less than a minute to say no, and they notify you well before the deadline. As for the slipcases, the monthly feature titles generally do because typically the offer is a pre-order. But other stuff that you order is hit and miss. I would say the newer the titles you're ordering, the better your chances are. But if you order Robin Hood, Sword and the Stone, Hunchback, etc you're probably hosed. Also please note that a few of the initial Disney Blu-Ray releases like Dinosaur and I believe Chicken Little never had slipcases to begin with. Disney used to have a service where you could call and pay a token fee for replacement slipcases (called "o-rings") but I believe it's discontinued.
Signing up for the club is a decent deal if:
1) You use the best possible sign-up discount instead of the default offer. I believe the code in the OP is up to date, but in case it's not,
check the blu-ray.com DMC thread for the most recent code.
2) You wait for stuff you actually want or for bundled monthly featured deals to maximize what you get for your mandatory full price purchases
3) You cancel once you've completed your commitment (there is almost never a case where it costs less to buy stuff full-price from DMC than from Amazon, so as soon as you've finished your commitment you should quit)
I've been through I think 3 or 4 full cycles and it's been great for building my collection.
