I use HT all the time. It speeds up my rendering times immensly. For instance....

My 4.4GHz E8600 rendered a scene I created in 6m 6s.
My 4.0GHz i7 920 renders the same scene in 3m 9s with HT off.
My 4.0GHz i7 920 renders the same scene in 2m 2s with HT on.

Real world proof in VUE 7 - no synthetic benchmark crap. Now just think of what it does when I have 2-3 day render jobs!

THAT is precisely why I bought the i7 vs. a Q9550 or something...