CDWOW are excellent for DVDs and customer service. I bought one PSP game from them (Wipeout) and it was delayed about 2 weeks, which I assume was due to general availability of anything PSP at that stage. They did email me a day or two after ordering to tell me there would be a delay though. I definitely recommend them.
BTW, has anyone seen any UMD movies on CDWOW? Play.com have loads, but I can't find any on CDWOW.