They should have had some negative effects with it and it should not be as common as it is.

Except they were more than a weak stamina potion.

I don't see why Beth couldn't code such a simple thing as speed and damage increase and speech reduction, or something like that.

I think they are trying to make skyrim seem like a isolated part of tamriel, cut off from the rest of the world.

Plus its far away from elsweyr, notice there aren't to many khajiit in skyrim? skooma in skyrim is watered down.

I forgot to add that there is a definite visual effect from Skooma, however it's only on dead Khajiits. Can you guess what it is?

The answer, my friend, is blowing in the wind.

I had hoped it had some sort of addictive effect, but alas it is just another restore stamina potion now.