I've tried this before too, it seemed pretty easy to install, which is a plus. Are there any performance issues with running Ubuntu this way? (actually, Ubuntu is the one I'm less concerned about performance-wise so this might be the way I go) I assume I can install it on an independent drive?
See my edit. ;-) Basically, there's a theoretical performance hit but I can't say it's noticeable. As for installing, it's completely native. There's a folder C:\ubuntu which contains two (interesting) folders: .\winboot with a backup of the original bootsector for the uninstaller and .\disks, containing two huge files: images of the root and swap disks.