Updates to Team Fortress 2 have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:
Added Multicore Rendering
This initial release is aimed at testing compatibility, so the option is OFF by defaultTo turn it on, go to the Options->Video->Advanced dialog, and check the "Multicore Rendering" option
Other Changes
Several performance improvements to decals and client bone/flex setup
A variety of alt-tab and mode switch fixes
Improvements to the way the engine initializes surround sound, fixing some specific hardware casesFixed a crash on exit in Vista 64