He said Lion and up, not sure if there will be a paid option at all. I've got a feeling that it won't support hardware that didn't come with an earlier model (he mentioned the hardware that it supports but I haven't cross referenced the default OS for those).

They have been pretty crappy about people emulating it so I wouldn't be surprised if this is an easy way for them to make that even more difficult.

(honest question) - Is windows 8.1 free if I have a (full, standalone) copy of XP or Vista, or only if I own Windows 8?

Mavericks appears to be free for people with Snow Leopard (at least, that's what I read).

8.1 is a smaller update than Mavericks, which is itself a smaller update than Win8 or Win7 (in terms of release schedule and scope, not judging quality or quantity of engineering). Apples and oranges, so to speak.

Unless you're interested in Metro (nobody), is there anything remotely interesting about 8.1? Mavericks has some impressive battery and performance improvements that anyone will be able to use.

I'd be mad if I had to pay for 8.1. I would've happily paid for Mavericks.