I am a big fan of the linux operating system. I originally started working with Slackware in the 1990's, which I had downloaded from the Internet. Since then I have used a lot of linux and unix systems, but I now prefer the Red Hat distribution.
Linux has very much been a command driven operating system and has until recently lacked the user interfaces of the Windows world. Recent releases of RedHat, Suse, Mandrake and the likes offer great improvements in the desktop linux field (utilising the Gnome and KDE desktop managers) and are quickly catching up to Windows.
My latest linux challenge has been to setup my adsl USB modem on linux, which took me around 1 day to get working...