graeme_p - 9:26 am on Mar 25, 2011 (gmt 0)
Mandriva is pretty good at "just works", and its easy to configure - more so that Windows or Mac because even advanced stuff like hosts file and MTU are in the GUI.
I am currently using PCLinuxOS which is Mandriva based. Its a rolling release distro, generally reliable despite that and has a good community. Most things work out of the box.
It supports multiple desktop environments. I am using E17 which has some (minor) rough edges but is both light and pretty, but the most popular is KDE4.
A lot of just works is down to luck and your hardware. The surest way is to buy hardware with Linux pre-installed from a Linux specialist vendor.