OK, here’s what I wrote a few days ago, regarding the Mac OS X transition to Intel:
Rainer Brockerhoff wrote:

…Most Cocoa developers that didn’t call Carbon frameworks to any great extent, or that didn’t have to deal with complex binary files, were able to recompile their apps into the Universal (“fat binary”) format in a few hours or days. In contrast, most developers of Carbon apps of any complexity faced months or years of conversion.

I invited comments on Apple’s carbon-dev mailing list, and some people objected to the paragraph quoted above. In particular, Apple engineer Eric Albert wrote:

I’d probably moved more Mac OS X code to Intel than anyone else before the announcement — some of the iApps and a bunch of other apps, plus a ton of work in the OS — and of the code I’d worked on, the Cocoa apps happened to take more work than the Carbon ones. That was really nothing more than coincidence because the Carbon apps I was working on dealt with structured data better than the Cocoa ones, but there’s nothing inherently more complex about the Intel transition for Carbon than there is for Cocoa. Mathematica, which is most assuredly a complex Carbon app, took four hours to get up and running on Intel, faster than any other app I’ve seen.

The primary reason for some Carbon apps taking a long time to move to Intel was that they weren’t using Mach-O or Xcode at the time the transition was announced and both were required for Intel support.

Carbon apps already using Mach-O and Xcode came over to Intel fairly easily.

Well, that’s quite definite; I was wrong there. I was wondering why, though, and here’s what I found: the RDF is to blame…

Here’s what Steve Jobs said at the WWDC 2005 keynote, where I was physically present, and quite near the front too:

So, let’s take a look at this again: Widgets, Scripts and Java just work. Cocoa apps, literally a few days and your Cocoa app’s going to be running with an Intel version. Carbon apps, it’s to be a few weeks, a few more tweaks, although there are exceptions to that although we maybe overstating it here, which we’ll see in a minute. And and in Metrowerks we don’t know, you’ve got to get to Xcode. So the key here is getting to Xcode.

And I distinctly remember the same point being made later in the reserved “state of the union” sessions: click a checkbox in Xcode, “boom” for Cocoa… not that easy with Carbon.

There it is then. I don’t have any Carbon apps myself, and didn’t have to migrate anything from Metrowerks CodeWarrior either, so I thought Carbon was to blame for stuff like the Adobe Photoshop delay. I’ll update my original post below; thanks to everybody who sent in comments.