Carnival hit it out of the park with Guy's Burger Joint.
What 2.0 actually amounts to is fuzzy and not all are created equally.
The new pizza is great and the pizza on Sunshine the best of all. Part of 2.0 or not?
Blue Iguana Tequila Bar and Blue Iguana Cantina are separate. ThirstyFrog Red is available on all (?) ships now.
I think they are improvements, some of which are better layout and higher efficiency. I also think some of those improvements are also trickling down to non 2.0 ships.
Would I book a cruise just for any? Probably not and maybe the opposite. Booking the pre 2.0 ships for nostalgia and for a few last flings while still available.
So I think they are neat and offer customers additional choice, including to stay with the old - at least for a while.