Mac OS X programs that will be the most hardest to port from the PowerPC to the Intel x86 platform will be applications written as Carbon applications. This includes programs like Microsoft Office and Adobe Photoshop. Carbon applications include old Mac OS 9 code and will be more difficult to port than Cacoa applications, which are completely written with Mac OS X technology.
Serlet said that developers should work towards a single SKU (stock keeping unit) instead of separate versions for each processor.
"The goal is to have one box in the store," he said. Apple refers to these types of applications as "universal."
He even suggests that developers might have to rewrite Carbon code by hand rather than using Apple's automated Xcode tools. More info at eWeek