hi litchick, et al.

I have been using nutritional yeast for years... my elderly mom craves it as does my child and my pets... so it has to be good for something. Actually it has huge amounts of B complex vitamins and is a great source of amino acids. B vitamins are depleted by stress and are also healthy for our neurological pathways. That's why some people feel energized by after ingesting them.
I am not vegan so I use nutritional yeast in combination with other ingredients. It is good on popcorn with butter. I put it in things that I also use parmesian or other cheeses with. I put it in mac and cheese as an extra ingredient, and use it cream soups or in dishes like stroganoff or stir fry. Alone on pasta it would be yucky!
Two tablespoons is a serving, that's all you need. It is also supposed to boost one's immune system, but I think that's from the B complex vitamins. It's also good in vegan dishes like tofu, coat tofu in nutritional yeast and fry it or use it in tofu salad.
Happy cooking!