Depending on which sites you visit for DVD news/info, some state that the Director's Cut DVD also contains contains the theatrical cut. Well, it does not. So don't ditch your original DVD release if you want both versions in your collection.
Although I understand that the Standard DVD doesn't have the theatrical cut, the Blu-Ray does indeed contain both cuts of the film. From the opening menu you get to choose either the Director's Cut or the Theatrical Cut. Upon choosing the Theatrical Cut you'll be taken to a menu of what is essentially the old Region 1 DVD (extras, theatrical cut, etc.), except in Hi-Def of course. If you choose the Director's Cut, then that takes you to a different branching menu which contains all of the new goodies (new extras, director's cut, etc.). It's a wonderful amount of bang for your buck for those who have a Blu-Ray player, but if you're going for the Standard DVD than definitely hold on to the old edition for the theatrical cut and the extras. Actually, that brings up an interesting question, does the Standard DVD have only the three new commentaries or did they work in the old commentaries too, even though the theatrical cut isn't actually on the DVD?