Snow Leopard release arrived today. Installed in about an hour, and BtS 3.19 seems to play with no problems.
Everything seems nice and snappy, and all my usual apps seem to be in good order so far.
The only casualty I've found is my Epson R200 printer - it insists on using a Gutenprint (open source) driver with no monitoring/maintenance tools. As compensation, my Epson scanner appears to have become a first class citizen in Snow Leopard, whereas before it seemed to live in a little world of its own.