Apple does have a good record of moving their OS and software from different architectures. 68XXX to PPC to Intel was not a horrible experience. Having gone through three transitions I don't remember a lot of pain - but maybe I am repressing it!
My experience with HN comments leads me to believe otherwise, at least among professionals. :)
Microsoft Office was another drag on the Carbon library. They also chose to keep their applications in the old format even though they were told repeatedly from Apple that this thing was going away. Eventually they got their shit together and the Office suite for OSX is a best of show.
Userspace GNU/Linux is also pretty bad about this, despite the effort put in by Linux.
The biggest issues I ran into was always with the low quality edu based applications. So many of the issues we had with those apps were because they were created in Windows and ported half way to OS X, an old PPC version that did something special that the Intel version couldn't do, or the worst one using a special baked in version of Adobe Flash..
/shivers
Asking for friend ;)
The app wasn't a universal binary at the time. Which would be fine if the PPC version worked with the PPC machines, and Intel worked with the Intel machines. haha.
*Edit The windows version did usually work without issues. The OS X version eventually worked once they redid the whole application.
Edit: maybe I should explain a little. We were a educational software developer and doing multimedia titles. We had a home grown multimedia engine which served us well (at the time there weren't alternatives) but Flash came along and at the time they would license the engine as a C or C++ library, which we could embed. This would get us a capable engine with superb integration with the content creation tools.
If your application let students finish what they were doing without randomly crashing and losing everything, then it is leaps and bounds better than the MAP system.
The school had to extend the map testing by 2 weeks just because of how often it crashed and students had to retake it. My coworkers at other school districts in other states ran into the same exact issues. Then on Windows, it had to access a SMB share somewhere to dump data to a flat db... that would get corrupted sometimes when a students application froze up... haha. it was job security though.
Unless you rely on a piece of software that does not receive any updates anymore. Then you're basically screwed. I am rather annoyed that Apple is going to break backward compatibility yet again for no good reason. Intel Mac's perform a perfectly adequate job and Intel couldn't really screw Apple because they are a rather good customer.