Well just off the top of my head... jumping is one of the main things about Jazz so you should think about how you could make jumping interesting in 3D. The question is whether or not you should do the type of acrobatics seen in Sands of Time or perhaps something else.

Because Jazz no longer has to just go forward and back he should be able to move sideways quickly to dodge attacks both in the air and on the ground.

And seeing as you as you can now aim properly you should probably make that a bigger part of the game. Have enemies or triggers that you need to hit in a specific spot, etc.

One thing you should definitely do is have dense and compact levels because Jazz isn't really suited to vast expanses of landscape I think.