Ubuntu isn’t bad. Let me say that first. I’m not posting this to bash Ubuntu, but think twice before you just hook someone up with Ubuntu when he asks for ‘Linux’.
Ubuntu follows the mainstream. Look at what Apple and Microsoft are doing with their OS, Windows 8 is touch-focussed, and you can’t deny Mountain Lion looks a lot like iOS these days. When people ask for Linux they usually want to try something new that ISN’T a touch-focussed, big button ‘look how simple we are’ OS.
And because of its Debian roots, Ubuntu is a bit behind on schedule, to get the ‘latest greatest’ you have to look beyond it. KDE 4.8 is much faster than the earlier KDE 4 releases, it’s smooth and fast and lighter, and most of all, convenient. Or perhaps you want something REALLY lightweight, you can look at LXDE/XFCE desktop environments.
And if you really want to go for an Ubuntu derivative, there’s also Kubuntu and Lubuntu.
Again I’m not saying Ubuntu is bad, but I’m seeing a lot of people that literally CONFUSE Ubuntu and Linux. Ubuntu is a Linux distro, Linux is not ‘Ubuntu’. There’s much much much more out there, and while Ubuntu isn’t bad, it ain’t the best either. So take a look around!