I don't know how many people here will use it, but I've just got my main machine set up with a WinXP/Fedora Core 5 'dual-boot' and sharing various bits of data across the two OSes.
I've had FC5 installed for a while, but not been using it because my Wacom tablet wasn't behaving correctly. Some of the settings possibly still need a minor tweak, but the mouse is now acting as a mouse and is no longer refusing to go within an inch of a randomly chosen screen edge, so it's now usable.
Having moved all of my Firefox and Thunderbird profiles/inboxes from my C: to my D: in Windows (I have a small C: for things that have to be on there, D: for data and most apps and G: for games) I've now got Linux set up to view those drives and Firefox and Thunderbird are set up to share the profiles That means that whichever OS I'm in - Windows or Linux - I get the same set of bookmarks, the same auto-logins on websites, and one central collection of emails (instead of Thunderbird in one and Webmail in another).
I've also got all of my MP3s imported into Rhythmbox (Gnome's audio player). All I need to do is work out how to get it to read the small collection of iTunes encoded M4A files, or how to convert them to normal MP3s and I've then got my MP3s in both locations (although unfortunately not my ratings as well, unless someone has a plugin for that!)
Redhat Linux/Fedora Core has certainly improved a lot since I first used RH7.3