I bought this to replace a previous Dementor costume that got lost in a move over a year ago. It is great for Potter fans or just for a scary Halloween costume. I wore it to the opening of "Deathly Hallows Part 2" and got a lot of postive comments and reactions (scared a few people coming out of a different movie too.) I am a bit overweight and it JUST fits me so this is not an item for "big boned" individuals.
The one real drawback is the mask that comes with it. It is pressed paper and is basically just a blank face. You can buy a vinyl Dementor mask to use with it or do some other makeup.

If you do buy it I recommend getting the Dementor hands as well. Those really complete the costume. And have fun with it.