I keep hearing back and forth about HT even though Steinberg still appears to recommend disabling it. From what I read on other forums SL users disabled it using some applications that came with the Apple Developers tools. I now understand these will not work on Lion. I did find this, and am looking for the forums two cents:
. . . you can permanently disable hyperthreading by issuing the following command in the Terminal:
sudo nvram SMT=0
To re-enable hyperthreading, use the command:
sudo nvram -d SMT
Changes take place on a reboot . . .