Torsen LSD will, as stated before, run rear wheels on opposite ways when car is lifted and wheels turned by hand.
Torsen is good by being virtually bulletproof but on slippery conditions (snow, icetrack) it will not perform like a cluch-type LSD. Torsen needs some traction to "fight back" to be effective.
Thats why I installed Supra MKIII LSD tunit into mine. It´s bolt-on swap (you can swap only LSD unit, not the whole pumpkin). Supra has cluch-type LSD and of course turning one wheel when car is lifted, the other turns the same way. Cluch type diff is better when you are practicing your high-speed drifts on snowy streets during the night. Car is easily controllable with your right foot.
And for those who have open diff, go with MKIII´s. They are cheap as dirt and readily available.
Oh, almost forgot - MKIII diffs go for IS300 diff housing only.