Today I migrated my Quicken account from Macintosh to Windows. I would wish worse things on my worst enemies, but I have a bit of a temper.
I was able to migrate most of my data by exporting on the Macintosh side to a .QFW (I think) file, then creating a blank account on the Windows, and importing the .QFW account into the blank account. Finding that process took several tries. If that is documented anywhere, I'd be curious to hear where.
I'm moving back to a Windows computer (and I've had several personal computers on both sides) because Quicken, among other applications, is reputed (or observed in my experience) to run better on the Windows side. This migration has gone better than my last two personal computer migrations — which is not exactly effusive praise.