I have owned, and really liked, the Shelter 90X, (although it was on a Basis 2001, with a Vector arm). It is a great cartridge, and quite the bargain actually. It has incredible bass response, (tight, quick and deep). The mid-range has a nice touch of warmth, and the treble response is well extended. It is a great bang for the buck cartridge, and easily in the Stereophile Class "A" category.
There are only two downsides to it that I found:
One, is that the treble, (while very good, and well extended), is not as refined as some of the better (and waaay more expensive cartridges). I am being very nit-picky about that, so don't let that worry you.
Two, the background is not as deep, dark and black as I would have preferred. (FYI: It is good in this regard, but just not great.) This was my major concern with this cartridge actually, as I had gone from the Koetsu Rosewood Signature to the Shelter 90X. One of the strengths of the Koetsu line is their deep, dark, black backgrounds. However, I lived quite happily with the 90X for a couple of years before I finally decided to upgrade to my current cartridge, the Dynavector XV-1S, (and that only happened because my friend was upgrading to a Brinkmann/EMT setup, and I got a great deal on the XV-1S).
For $1,000, assuming it is in good shape, this is a no-brainer of a decision. Good luck with the 90X. I am sure you will enjoy it.