Now that I have been running OS 10.6 (aka. Snow Leopard) on my 2006 MacBook Pro for a week. I can offer my opinions of the latest OS X.
Twitter followers had heard me complain that my MacBook Pro was very slow with certain apps, including those that others had raved about for being improved and much speedier.
If you read my post, Snow Leopard Now Installed, you will know that I spent some time examining all the Extensions, Input Managers and Plug-ins, to ensure compatibility with OS 10.6 before I upgrading my MBP. So I don’t believe the application slowness was due to the incompatibilities of Extensions, Input Managers or Plug-ins.