Am now running Mac OS X 10.6 Snow Leopard

It's definitely snappier. Only issues for me are that the Logitech driver for my mouse no longer works (no biggie and easily worked around) and Google Gears (for storing Google Gmail/Calendars/Docs etc. offline) no longer works. Am sure updates for both of these things are just around the corner and are certainly not "deal breakers". So far, so good but will keep you posted!