I'm kind of a big deal in Redmond - New update!

Source Engine Changes (TF2, DoD:S, HL2:DM)

• Dramatically improved the dynamic model loading system's memory usage, performance, and stability
• Reduced memory usage on systems running Windows XP, Windows Vista, and Windows 7
• Improved alt-tab handling under Windows Vista and Windows 7 

Admin: this will be welcome news to most windows users (99% of TF2 community).