Image stabilisation has some pretty limited uses - namely situations where your subject matter is (relatively) still.
If I had the choice, for the same $$, between an extra 2 stops of lens light (1.8 vs 4) or IS, for the same price, I'd take the extra stops of lens light.
Sure, IS is nice, but when your subject is moving, IS does not increase the speed at which your shutter can move without photograpgic blur, rather, IS makes it possible for your shutter to move slower without blur due to the camera being held.
The extra stops are even more useful when you're attaching filters, such as polarizers.
IS helps but don't make more of it than what it is until you can tell animals and children to slow down for your camera because you have a "slow" lens.