Yeah, I bought the new edition, but I don't have the previous one to compare it to. It compares well with the original DVD release, however, in terms of image quality. As far as the new extras go, the commentary with Towne and Fincher is just so-so: the occasional observation is offered, but there's a lot of padding. Then there is a 90 minute documentary (that I think is new) broken into three parts about the history and present situation of LA and the water it imports. This doesn't have anything to do with the film except by way of background, but it's nonetheless interesting, with Robert Towne going along on some of the interviews. Finally there are the extras that have been available on previous editions.
No doubt all the extras will be on the coming Blu-ray, which will, of course, offer the best image quality yet.