Actually, in S1 there weren't really any limitations, only advantages. Think V-Vocal integration, only with Melodyne, a far supperiour pitch correction tool IMO, from what I have seen of it. I love Melodyne so this is perfect for me.
A really cool thing about it is that it uses whatever version of Melodyne you have installed. So no limitations to the software either, just great integration with your work environment.
And from what I understand from Seth's and Dan's subtle teases, it will be even better than what S1 can do with ARA and Melodyne so this should be a pretty cool upgrade for those of us who utilize Melodyne extensively;)