VR Zone did some Hyper-Threading tests on a Core i7 system with a Radeon HD 4850 X2 graphics card to see if this feature of the Core i7 processor offers big performance gains. The results were mixed, in some tests the gains were huge but in games it dropped the performance.
Certainly, 3DMark Vantage loves to have more threads as we can observe a significant boost on the CPU score. As for Crysis Warhead and Far Cry 2, we saw a small drop in FPS when HT is enabled. On the 3D content creation part, CineBench 10 registered a neat boost of about 17% when HT is enabled. Overall, HT is good for numerous applications out there that are multi-threaded but we aren't seeing any benefits for the latest games out there now.
Here's a quick look at the results of Hyper-Threading: