I can also see the differences between act 2 in D2 and D3. Lut Gholein really felt as a little tradestown based near the sea. Caldeam feels like the jewel it's discribed to be. Also the Oasis zone is completely new and the sewer levels are actually watery. They are deffo not the same as the sewers in D2. However, the desert theme is pretty much the same and the Shadow Realm is exactly the same as the Arcane Sanctuary.
Act 3 has some new zones like Stonefort and both the bridges. Although they are in the same style as in D2, they both deffo gave a new experience. The athmosphere in the whole act was a lot different from D2 aswell. You do feel like your on a battlefield. The towers are also completely new.
Lots of new stuff, imo. It's just that old stuff is so easy to point out.