DDD is a reliable company, but they don't get in any hurry to ship. Their prices are extremely competitive (except for Superbit releases) and they have never not shipped me something out of probably 20 orders. They usually have very hard-to-find stuff and extended versions you never knew existed. The search engine is better than most places.
The only real weaknesses are that their descriptions are on the Reader's Digest condensed side (oh crud, most of you don't have a clue what that means
), so sometimes you have to check twice to see which version you are getting (but hey, there's always IMDB to get that info) and that if you pride yourself on being the first with the latest releases, you won't be.