Yea, most of the time (as with the Great Nor'Easter) the only noticable change from one SLC to another is the fact that the Great Nor'Easter's station does not lead straight into the lift, but there is a short 90 degree right turn.
About roughness, the newer are better than the older, that's for sure. But it is still up to the park to ensure the smoothness. Some say that with the addition of new padding, what WAS the smoothest SLC (Serial Thriller, SFO) is now just one of the pack of hang-n-bangers.