Xandros is a nice, easy to install and slick system...but they want you to pay extra for "premium services" such as downloads of other open source programs (that have been tested and rpms built for xandros)... I find it too easy to break the system when you start adding apps or tweaking the system.
I have used both xos 2 and 2.5 (busines edition)...I would never buy it...

KDE still rocks!