As George knows I tend to agree with him, but using the correct aluminum drive shaft is not an issue in our trucks. I have used one since the ATR started selling them way back in the day. Also because we split our power front/rear it even gets less abuse than our f-body RWD friends. I have many F-body friends that us PST and Dynotech aluminum shafts rated to 1,000 hp.
Aluminum shafts are a third the weight of a steel and half the weight as a chromoly. Of course the CF shaft is about half the weight of the aluminum and handles as much HP. One of my NOS powered, 10sec SS Nova friend broke two steel drive shafts this summer because he though they were less expensive way to go (Obviously not thick enoungh wall size). He ended up buying an aluminum one. He will attest that you don't want to break any drive shaft as it tore the under side of the floor and hump up pretty bad. Cut right through some of the floor.
George's guy is right about the fact you can build a stronger steel shaft than aluminum. It's the extra weight that most of us don't like. For every 1 lb of extra weight on things like cranks, drive shafts, axles, converters, etc., is like adding 8 -10 lbs under rotation, to your vehicle via loss of hp.
John