Obviously I have never used Xandros and am curious as to why it is your preferred OS.
It is really easy to install. I was a n00b back in 2004 when it came to Linux, but I found it easy to install even back them.
If you're familiar with the GUI of Windows, then you should be familiar with the GUI of Xandros.
It's pretty easy to install 3rd-party apps. You can use either Xandros Networks (like Linspire's CNR, but quite a bit of the stuff available in Xandros Networks is free to download, while you have to pay $20/$50 a year to join CNR) or the console using apt-get. I've managed to install and use GNOME on Xandros 3.0. The only thing about Xandros I don't like is the built-in CD/DVD burning in the Xandros File Manager, but it's easy to use apt-get to download and install K3b.
Xandros 3.0 Deluxe also comes with a built-in firewall.
It is also easy for me to install certain Windows-based apps (such as iTunes 4.9) by using Crossover Office. I've had mixed results with Transgaming Cedega, though. But these days I don't play much games on a PC. If I do play a game on a PC, it will probably be a classic console emulator such as Genesis or SNES...I have ZSNES installed on my Xandros machine, and it plays SNES games really good...almost as if I was using an actual SNES.
I just can't put my finger what what is it that makes Xandros my preferred OS...if I had to choose one thing, I guess I would have to say it's the one Linux distro where it's been really easy to get my winmodem working. Once I get my kernel headers compiled, installing the winmodem driver is a snap (it has a Conexant HSF chipset).