I have both developer previews installed on my mac, whilst I think Windows 8 is great, I still think OS X is better.
Windows 8 on a desktop is just not nice to use, and for me (and no, I'm not a noob) its actually quite confusing. For instance I don't have a clue where to access my non metro apps, after using windows for year you just get so used clicking start and accessing everything there... Now it's all very inaccessible. I think this is going to be a huge problem for non-nerds I.e most people who use windows.
On the other hand I installed splashtop streamer on it and used it on my iPad and it was a much more pleasant experience, and I think windows 8 tablets will be even better as the OS is optimised for touch even more.
I much prefer the apple way of doing things, personally I don't want to run a full version of OS X on my iPad, it just wouldn't work as well (unless it was hugely optimised for touch)
I think keeping everything very closely integrated is a much better way forward.
Bottom line, I don't want my desktop to have a OS for tablets and I don't want my tablet to run a OS meant for desktops, I just want them to be synced without me having to do anything.
Sorry, Wasn't expecting to write much