1. I use Ubuntu Linux. It was the one i was introduced to first.
I tried out the kubuntu version because someone said it was closer to a familiar windows environment. Personally i hated the KDE interface, and have since preferred GNOME.
2. I use it because i'm tired of servicing my windows machines. No viruses, and everything is organized in a way that's understandable. I also like the helpful community, which is not unlike the chief delphi community in some way's.
3. umm.... well, that is really up to opinion. I have a few quirks with GNOME here and there, and a few other various things i don't like. Advantages... well opinion again. No viruses, clean packagement, open source software, more intuitive feel to it.
4.
http://ubuntuforums.org/ https://wiki.ubuntu.com/LoCoTeams
5.An OS should be reliable and not crash when you need it not to. However, there should be a rather easy way to fix human error, or at least a way to fix it without having to reinstall it.