Running Debian "testing" on all my machines, Scope's been boxed for over a year due to renovation works at our house. Moving next weekend, then start setting up the studio again... It will have the only XP machine - the Scope host.
If you're gonna switch OS, may I ask why?
Many people I know think they're getting a "free Windows-like OS" with Linux, not realising it's a totally different concept requiring a different workflow. If you plan on going Linux, cudos to you, and get ready for days of web searching and reading manuals. If it weren't for Scope I'd never look back, but it's taken a while for me to get the hang of "linux". You need to be willing to crawl and learn to walk again before you start running.
Another misconception is that the mouse is the one and foremost interface for a computer, which often leads to cold showers for those switching to Linux. Many things are just so much easier from the console, and when you learn how to use a keyboard, options are legio. Think of stuff you do daily and takes 10-15 clicks while intermediately eye-scanning through dropdown, popup and I don't know what other menus. On the console, you'd group that sequence of instructions in a script which can now be called by other events (scheduler, single command, click a link to it) skipping all the GUI bloat and, why not, run it on a headless (no monitors) server. On another note, KDE and Gnome are providing frontends for these console tools (wifi configuration, mounting disks etc.), but nothing beats the console. They just couldn't stuff all the options available on the console into a UI, so you end up making little scripts (remember .bat files?) doing all the work for you. No need to know all command line applications and their options, just when writing the script it takes a moment of informing yourself - after you don't need to remember eh.
So, before you switch, keep in mind you'll be spending at least a year solving riddles before getting productive. Countrary to Linux, OS-X will work OOTB, but it'd still be a new OS to get used to. Things are simply done differently on each OS.
Linux distributions often offer versions which run directly from CD/DVD, trying 2-3 different ones can give you an idea on the differences, driver support etc.
64studio is a Debian-based distribution aimed at media production,
Ubuntu Studio is Ubuntu-based. "-based" here means that they are Debian/Ubuntu but bundled with different software packages and compiled with slight different options, like realtime kernels (near absolute system priority for apps/devices that shouldn't be interrupted).
I don't advise getting Linux as your main music production OS, but I will sure keep my current Debian systems in the
farm, euh basement, living room and bedroom, and have one with a proper audio interface next to the Scope machine to control the others and their
applications...