Yup specialist are not so great in C3 or PTW as they give 1 commerce, 1 beaker and there are no Civil Eng.
They are very important in C3C, even at low levels. I played out civ4lyfe's 700AD and late in the game I had 600+ scientist (1295 pop). Some of the MA techs could be done with 0% slider.
Scientist are the most for the buck as you get 3 beakers, rather than 2 gold. These of course are regardless of the corruption or the slider. Once I get rails, I maximize as many towns as I can to make food so I can have the max scientist in that town and feed it with the min citizens working.