I wish I could remember the quote well enough to search accurately for it.
And while there was a dead period due to the technically deficient underpinnings of the late Classic MacOS, before that, the Inside Macintosh days, I hear folks loved programming Apple too.
After having been deeply involved in the Mac dev community for the last 10 years, the implicit claim that Apple is a company pro developers do not love working with sounds, frankly, a little bizarre.
Our first app was built using 'unsanctioned' technology, PyObjC (before PyObjC shipped with 10.5); the app would have never seen the light of day on the iPhone, but then again, we would never have built it in PyObjC for the iPhone to begin with. Everyone we've ever met at Apple has been supportive from day one, and we owe a lot to many of those people.
We have not shipped any iPhone apps, so I can't say how I'd like that, but as a Mac app developer I love working with Apple.
That said, with OS X they really became a lot more developer friendly just because they adopted a UNIX base. At this point, I'd say they're the default platform for ruby/web development. Look at all the rails job postings for small startups promising 30" Mac Pros, etc.
But I dont think it was purely a codewarrior issue. The overall apple OS at that time was simply terrible and 10 years behind windows (i wont even count how far behind unix they were) -- they still could not get multitasking to work right. Which meant that any pointer error causes your computer to hang. And when you are coding for a data structures class in C all of your errors are pointer errors.
So I am sure a lot of developers abandoned the mac platform around those times, but maybe many of them are coming back now.
I'm pretty sure that it was dominant at the time. I remember reading a lot of examples that used it.