Good idea! I've just done exactly that. Not for the first time, but having tried
other configurations in the last couple years I decided that dual-boot was the
best way to get everything running properly.



A couple of things to watch out for:



install Windows first, because it insists on overwriting the boot
record. If you put Ubuntu on then Windows you'll have no way of booting into
anything but Windows. Ubuntu is much politer, it lets you choose via the Grub
menu.



Have between 10 and 20 gig for your Ubuntu root partition.



If you've got enough disk space you could set aside another 10 - 20
GB for trialling the next release of Ubuntu, or other distros, or Kubuntu, etc.
(Just be careful now you let different OSs use your precious data - especially
Alpha releases).



I think Windows 7 also needs between 10 and 20 GB. iTunes can be
hungry though, depending on howmuch musicetcyou keep on it. It seems to
duplicate everything. RhythmBox is better in that respect , but as you or
someone else said it doesn't transfer playlists, nor videos (I'm going to give
iTunes one more chance when I get round to it).



Your swap file should be twice the size of your installed RAM, no
more no less - that's the recommendation I've seen anyway.



And of course, have a separate /Home partition, occupying the bulk
of your disk.



That's my experience, anyway, and I hope it's useful.