Hallo Michael,
completely switched to 9.6 UB on MacPro and even upgraded my old G5 to Leopard in preparation to be able to install LW 9.6.1 UB-64 there too.
As this will be the minimum Hard- and Software combination for 64 bit LW on a Mac, I would assume that many G5 users are considering to upgrade to Leopard as a last investment in these machines.
What bothers Mac users most imo is the lack of 3rd party UB plugins and additions (shaders, nodes, ...), and I truly hope that this will change with CORE (but sadly I'm not _that_ convinced that this will happen).