For those who like to have a fast and lightweight Ubuntu system installed in their machines, Lubuntu is one of the best choices available. This is an Ubuntu based distribution which uses LXDE as its desktop environment and works stunningly fast even on old hardware.
One of the drawbacks of Lubuntu is its unattractive UI that has kept it away from those users who want a 'glossy' and polish UI. Hopefully there are some UI improvements planned that you will see in Lubuntu 12.10, releasing this October.
The Lubuntu Artwork team posted on their blog, "The Lubuntu Artwork Team is not sleeping. We're getting some UI revamped elements, improving the current theme and getting it to a higher level. Among the icon theme (being exhaustely developed), the GTK2 / GTK3 themes had been redesigned (for both looking better and integrate between them)."
This screenshot shows how PCManFM – the default file manager for Lubuntu looks. Seems quite impressive work. Also this will mean better integration with Gnome apps.