To be clear, U3DXT still does not work with Unity 5. How did I verify this?
I am on Unity 5p1 using Xcode 6.1.1
I created a new project, switched to iOS, built and ran successfully
I downloaded the very latest U3DXT Pro from the asset store
I changed none of the import settings for the package
(I found it odd that Unity 5 still had to fix up some of U3DXT’s scripts!)
I built the iOS project without error
Building in Xcode results in 20 errors, with the famous header ‘Undefined symbols for architecture armv7’
We shipped a game that is live with U3DXT, but this “support” method is abysmal and it still doesn’t work.
Unless you see a reply from U3DXT that shows how to fix this “out of the box” issue, along with my verification that it worked, please take my advice and do not buy or use U3DXT. It is dead.