Someone posted that hyperthreading actually hurt performance in warcraft.

I decided to disable the logical cores in IS Boxer Toolkit, and only run with the physical cores as an experiment. IS Boxer labels the cores 1, 2, 3, 4, 5, 6, 7, 8... where 1 is what most refer to as core 0 etc. So the physical cores are 1, 3, 5 and 7.

Long story short, I personally get slightly better performance in warcraft without the logical cores. But the difference is very marginal. And I only tested for a short period one evening. My i7 920, without hyperthreading runs the game quite fine, but it ran it very well with hyperthreading too.