I think most people would experience the terrible load times of the Stalin and never take it out again. It was actually an open country breakthrough tank which is a complete opposite to the way Tanks operate in AH. Not just that but the Stalin had a rather poor aiming system which negated much of the long range advantage the big gun gave it.
Had the JS been fitted with the far better 100mm gun, and had a better sighting system, this could have been a really great tank. As it was it was still the right tank at the right time, however, Im not sure it would fit into AH very well.
But I guess it all depends on modeling.