“However, I did cheat a little. On my original iMac, I actually managed to get a complete working replica of my old PC running in Parallels.”

That’s exactly what I did with my old Amiga setup (using UAE, obviously) when I switched to Linux in 2005. Used it on and off for about six months. The only problem was that networking didn’t work very well in UAE back then, at least on Linux. But it definitely helped with the transition. I’d recommend anyone switching OSes to do the same. The virtualization options are vastly better now anyway.

“There’s Steam on the Mac of course, but half my Steam games are Windows only.”

Although I never had a Windows machine, I’ve picked up the odd thing in a bundle or free giveaway over the years, and Steam works fairly well under WINE on Linux. Would that be an option? The performance probably isn’t quite as good, but at least it’s more convenient than dual-booting.