Well, just played with Curve 4 on hip and sprint and Curve 3 on ADS and got a We Ran Out Of Medals!
Curve 4 is beautiful on hipfire. The previous curve in comparison felt a little bit wavy in comparison, like slightly floatier if that makes any sense... curve 4 feels the closest to PC I've ever felt playing D2. Incredibly responsive, no over drift when I make sudden flicks or changes in direction with the mouse, just feels very precise and true.
I'm going to give it a few more games with Curve 3 on ADS. I'd come from your standard curve so I think there's far less aim assist with this one (which I prefer) but will have to get used to before I can give more detailed feedback.
EDIT: Second game - 42 defeats and 7 KAD. Definitely liking number 3 as an ADS curve. Again, very responsive, very true and I've noticed a significant decrease in reticle drift when a player runs across the crosshair while I'm aiming down sights at another player. Really, REALLY enjoying these so far.