I'm a great fan of GITS, and have seen most of its incarnations. The digitally-remastered version of the original is available as an "extra" on this DVD, and I think I prefer it to the "Redux" version, although the new CGI is interesting. It doesn't fit all that well with the original cell animation, though. For fans I'd say it was still worth a look, especially at a reduced price. But if you've never seen the original I'd go with that.
I agree with several others that, whilst the improved sound and visual resolution (and colouring) is welcome, the CGI just distracts from the flow of the movie. Don't be too put off though: it is worth watching, as the visual quality of the original was fairly low compared with current standards and it's nice to see it all looking brighter and clearer.
Note that Amazon have (as of Oct 2010 anyway) put the Synopsis for GITS2: Innocence rather than for GITS2: Redux, i.e. they give the impression that this is the recent sequel, whereas Redux is a re-working of the original movie. Not surprising given the obviously confusing names: both are called GITS 2 despite being a different product altogether. There are also several rather confusing editions of the two films: for example a Blu-ray double box set of both Innocence and Redux, which adds nothing to the individual DVDs except a bigger sleeve; the two movies, individually packed; the original is still available; and the separate Blu-Ray versions of each film. All appear to have the same review and synopsis regardless of which is which!