10.8.3 isn't out yet. It might be coming soon though.
My less capable 2011 21" iMac i5 with 32GB and a 2009 Mac Pro with 64GB both run 10.8 and neither of them has this "banding issue" with FCP. Obviously, it is a problem -- otherwise that thread would not have got the attention it did. Maybe I'm just lucky?
I will have to read that thread again to see if the issue was only inside FCP (it has been a while since I stopped reading it). If that is the case, you have to remember that FCP's Canvas only shows a low-res proxy anyway.
FCP is all about concentrating on the flow of your story. You should not use the Canvas to make decisions about picture quality or color fidelity. If you really need that in a live post-production environment because clients are being picky, then you need to be connected to an external broadcast quality monitor driven by a qualified interface.