I know apple makes this claim, but I question the truth of it to some extent. Why does it take so long for some programs to go to Intel. If it was really just as simple as sticking the code in the Xcode Compiler, why would Adobe and Microsoft wait until a new version of Photoshop and Office before releasing Universal Binaries for the programs. I remember a VP or someone else of high rank at Adobe saying that making UB's for their code wasn't as easy as Apple makes it seem.
I'm not necessarily saying that it's not as easy as Apple says, but I can't seem to see a reason that it would take this much time for a UB if it was as simple as sticking it in a different compiler.