I got my copy this week.
The Amazon reviews were a bit harsh. I've seen better, but I've also seen worse. Much, much worse, like
The Bell Jar.
The DVD actually is widescreen, but it's widescreen NON-anamorphic, and the movie was apparently only shot at a 1:1.66 aspect ratio. I'm guessing the reviewer above was watching the image stretched on a 16x9 monitor, hence his comment.
Sound is mono (and I'd imagine it was filmed that way back in 1977), and the picture, although with dust and debris, is significantly clearer than the old VHS release, as evidenced by the two captures below (borrowed from DVD Talk):
VHS:
DVD:
As a film adaptation of a Sondheim musical, though... it still pretty much sucks.