Just got this from NVIDIA:
[quote]We have found that some games running under Windows Vista enable 16x coverage sampling antialiasing (CSAA) when 4xAA is selected in the game menu, resulting in deflated performance on Geforce 8800 cards.
The problem occurs with NVIDIA Vista drivers 100.54 and later.
The same effect will occur in future "Release 100" Windows XP drivers.
Affected applications found to date include:
Battlefield 2
Battlefield 2142
Sin Episodes
Half-Life 2
Half-Life 2 Lost Coast
To set standard 4xAA in these applications, please set 4xAA in the game, and also enable “Enhance the applicationâ€