Think I'll have similar luck with my parents?
I don't see why not. You have to make sure the situation is perfect. Make the interface familiar as well as familiar programs. My ex only ever surfed the web with firefox, used openoffice, and media player classic in windows. The equivalents for linux for her was basically the same offering of software that she normally used in windows. I got her up and going with kaffiene for media player classic like media player. Also got her up and going with kde as her DE along with the mass storage taskbar addon in kde. After that computer on the desktop was easily understood as my computer, and the home directory as the equivalent of my documents worked good for her too. She really liked having an admin password and a user password. She totally digs having extra control with the security of her system that goes past just locking the desktop.
Use kde 3.5.10 for your parents. Kde is easy to modify to make it look like vista or classic windows (good for making users more comfortable).
Linux doesn't work in all situations for first time users though. It does work great for first time users when they don't have their own legal copy of windows (like my ex, they're usually the ones who are happy for an alternative and eager to learn). If you're parents are going to be messing around with linux install the kubuntu 8.0.4 release, and install with the wubi windows installer.
This will setup a dual boot system without wiping out the windows boot loader with grub (kubuntu will just get a bootup option in windowse's bootloader). This is the easiest way to setup a dual boot system and the fastest way to restoring a system back to normal when removing kubuntu. After installing kubuntu, make sure to install firefox.
With this you'll be able to dual boot and show your parents what's what. But, i wouldn't make them switch. Unless they need to reinstall windows and don't have a legal copy, or if they constantly get viruses and are tired of maintaining their computer when your not around. These are the only reasons i would try to interest someone in switching.
A good joke. "have you seen the latest ubuntu?", "i don't like pokemon."
