So, what happens if you plug a non-Apple USB keyboard into a Mac running MacOS? Does it get all the keys right?
More-or-less. I think the MS Wireless one actually has explicit Intellitype software for Mac, which handles that, and there's very easy-to-find software out there for swapping Command and Alt from the Windows Way (or now I think of it it might actually be in Sys Prefs -- but since there are so many Mac users doing that, it's easy to get.
The problem I had when I switched is that there are still so few switchers (comparatively to people who grew up on Macs because their family had one or they were in graphic design) that if you Google it's not as easy as it should be to find the keyboard hack to bind shift-2 to @. Actually, should glance at David Pogue's book on Tiger Switcher Edition (O'Reilly), because that would almost certainly cover this sort of Mac-as-a-Second-Language problem.
Regards, R