I've been playing.
One of the essential features of a Linux user appears to be the "how does this work?" mentality. In fact, it might be the defining characteristic. The more experienced people (they're the ones who have figured out why you should back up) are called "dev's", and spend their days creating new things for other people to try to break. Disappointingly, when the users are successful, there isn't the "gotcha" that usually happens in this electronic game of hide and seek; all we get to do is fill in a bug report.
Anyway, having a whole 18 months experience in Linux, I figured it was time to try breaking exploring something else. I've already got a dual boot with Vista, but it's more of a legacy of times gone by now- the only real reason to use it is to see if it really takes that long to boot up (it does), and to see if the fingerprint reader really works (not supported in Linux; good on ya Dell!) So, I figured if dual was no sweat, why not try triple booting? Ubuntu is nice, and has it's strengths, but the mono debate and the Ubuntu One stuff are making me a little wary. I've been backed into a corner regarding my options before on a PC, and don't want it happening twice. While I'd played with VirtualBox, and got a system running, it wasn't the same as a full install, and - well, I've backed up now, so how bad could it get?
Apart from a /home backup, the other useful bit of data before you start is a wee file with the package list. This is one site that documents the process nicely: http://kevin.vanzonneveld.net/techblog/article/restore_packages_using_dselectupgrade/
Debian was my choice. I had a look at Fedora, but the installer was a bit keen on taking up the whole hard drive. LVM is a great idea, but with an inverse amount of documentation to its brilliance, I'm fairly sure. The notion of getting locked in was driving me, and Debian has freedom to burn. In addition, I figured it couldn't be too different to Ubuntu, given it was the originator. You can have too much change, after all...
First up, the partitioning proved to be more challenging than I expected. Sharing the swap partition is well documented and was supported in both installs. A separate /home partition makes good sense, and it's well documented. What's not so well documented is that - like toothbrushes- it's not a good idea to share /home between distros, even though that's where your data is. The problem is that there's a heap of hidden files and folders, including the Gnome settings. I'd run into this before with upgrading; ndiswrapper files left behind caused me a reasonable amount of downtime, so sharing my /home was a no-goer.
So, I ended up leaving the /home folder in the install partition, and creating a separate data partition, mounting it separately at /mnt/data/ . That's where all the stuff I want to share across installs goes, and it's easy enough to set it up to mount automatically on any new install.
Next up was GRUB. Grand and Unified, but again not fantastically documented. Grokking man pages is OK for a bit, but when I'm trying to figure out an installation, partitioning, and a new OS I'd kill for a walkthrough (incidentally, there aren't any on how to dual boot distros that I could find). I ended up installing Debian (without too much difficulty). Unfortunately, Debian lenny doesn't support ext4 without some fiddling, so wouldn't find my Ubuntu install and add it to GRUB. I could get back into my Ubuntu partition with a live disk, but reinstalling didn't work without deleting /home. I was getting a white screen after the login; I'm pretty sure it was the compiz drivers not being installed, but the xorg settings requiring them. Once again, feeling very virtuous/lucky/relieved that I'd backed up, I reinstalled with a format of /home, and everything worked fine. By reinstalling Ubuntu, I got GRUB2 again, and was able to get both installs automatically added to the GRUB menu.
Debian is niiiice. If you're thinking of trying a new distro, I'd recommend it. I always change my desktop background to one of my recent photos; no problems there. Epiphany is the default browser, but Iceweasel is also installed, and I like to be able to sync bookmarks, so while I'll use epiphany when I can, Iceweasel is more compatible with Firefox and seems to run the add-ons without any problem, whereas epiphany has its own addons, so is much more limited. They're both fast, and I'm thinking I'll have to change to Iceweasel in Ubuntu now.
Wireless was a bit of an issue- now there's a surprise. Getting the Broadcom drivers for my wireless card, again, not too difficult, although it helped that I've broken that before now. Gnome Network Manager is installed, but the System/Network app modifies your etc/network/interfaces file directly, and NetworkManager won't manage any interface that's mentioned in the etc/network/interface file... it took a wee bit of figuring out. I guess you can't please everyone, and it's not like it was a huge issue. My assumption when I started this was I'd learn something, and I've done that.