vivkr wrote on May 14th, 2012, 5:53am:and I missed the (gm/Id) part of the question, looking only at fT...
I guess if you are trying to look at both (gm/Id) which gets maximized for low Vgs-Vth and fT, which gets maximized at higher Vgs-Vth, then you might end up with reasonable Vgs-Vth at the end. So my comment about it being difficult to drive in that much current may not hold.
As to whether the optimum scales with technology, I would expect so for the reasons outlined earlier.
Vivek
My experience in the technologies its usually at a quite low overdrive, but as you say its technology dependant, but also dependant to the particular device type and sizes you're looking to use.