While I can't speak for the LS 9000 directly, I recently got my hands on a Coolscan 8000, which uses the same carriers as the 9000. The mounted slide and 35mm film strip are OK- they work, the film one is a bit flimsy, but can certainly get the job done.
The 120 holder, on the other hand, is utterly useless. I simply can't believe that a machine that at the time cost some $3k would ship with something like this. Your films, regardless of how straight or flat they may be invariably will bow, and, given the narrow DOF of the Coolscan lens, you will get soft scans. I knew about this issue before I bought the scanner, but I thought I'd test it- trust me, it's ridiculous.
The glass holder is better- I got the G (not the GR-rotating) version, and for the most part, it holds the negatives flat and in the plane of focus. Using the masks takes some getting used to, but once you figure it out, it's not that bad. Still, coming from the 5000, which is really a plug and play scanner, I have found the 8000 to be more of a pain.
Another bit of advice, and I'm sure you'll hear this from others, is to get Vuescan (or Silverfast, if you can afford it). I spent quite a bit of time working with Nikon Scan (on a mac), and found it to be limiting, buggy and rather useless as it would invariably crash as it pleased.
Enjoy your new scanner.