I believe that at the very least, if you put them on separate hard drives you should have no problem dual booting between Ubuntu and Windows 8 (or 7 of course).
On my desktop machine at home, Windows 8 Release Preview is on one drive and is totally unaware of any other operating system's existence. Ubuntu Studio is on the other, and all I had to do after adding the Windows 8 drive was run an "update-grub" command.
Of course to install Windows 8 I had to connect only the hard drive it was going onto during the installation. I don't go into Windows 8 on that machine. The only thing it's used for is to run World of Warcraft for my brother. If I didn't have issues running WoW in DirectX mode on an ATI card, it probably wouldn't be there at all (or if Blizzard weren't letting the OpenGL 64 bit bugs in WoW remain forever, even though Mac users are experiencing the same issues).
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