Having played the demo at BlizzCon last year, I can tell you that he's not joking. The loading times from area to area are extremely impressive considering all that's going on in the game. We sure have come a long way since "insert disk #8" haven't we?There aren't any loading screens. Personally I think it's amazing and I don't understand the magic the programmers have worked, but the game is instant or near instant. The same is true for initial game load. Start up the game, create a character, click a button and the game world shows up. No waiting and no real discernible pause. Mileage may vary slightly of course, but it would (from what I've seen) be in the realm of a second or two second pause at most.
The loading screen between acts (which last 1-4 sec) is hardly a bother.