Jeff's got the skinny and some excellent analysis. Not sure I need 'em (my original 1e PHB is still in decent shape) but as I and those books get older, I can't help but think that having some "stunt copies" for actual use is a good idea.
If you don't own a copy of the 1e DMG, and you play any sort of fantasy RPG at all, you owe it to yourself to pick up a copy. It's got a huge range of useful-at-the table info, like the reputed magical properties of various gems (pp. 26-27), the cubic volume of rock miners of various races can excavate (p 106), the healing properties of herbs and spices (pp. 220-221), and those wonderful 1e artifact-level magic items. Plus, some of the best art of the era.
If I could own only 1 RPG book, well, ok, I'd probably go with the 1e PHB. But for running a game, designing campaigns and adventures, or just pure inspirational reading, I've not seen anything yet that can touch the 1e DMG.
UPDATE: Here's a link to the actual product description at WotC's page.