[worstspotgain]

The 9->X trapeze act was a colossal success, but in retrospect it was brutally risky. I can't think of a successful precedent involving popular tech. The closest parallel is OS/2, which was a flop for the ages.

A large amount of transition code was written in those years. One well-placed design failure could have cratered the whole project. Considering that the Classic environment was a good-enough catch-all solution, I would have also erred on the side of retiring things that were redundant in NeXT-land.

Resource forks were one of the best victims, 1% functionality and 99% technical debt. The one I mourned for was the Code Fragment Manager. It was one of Apple's best OS9 designs and was massively superior to Mach-O (and even more so wrt other unices.) Alas, it didn't bring enough value to justify the porting work, let alone the opportunity cost and risk delta.

[sillywalk]

The Challenges of Integrating the Unix and Mac OS Environments (from 2000)

https://www.usenix.org/techsessionssummary/challenges-integr...

[tambourine_man]

I'm still mourning file name extensions and the loss of the spatial Finder.

[kzrdude]

Me too and I switched from Mac to Linux in 2005.