LXDE is a light-weight desktop environment meant for low-end computers or minimal desktop environment enthusiasts.
Ranked in these QuestionsQuestion Ranking
Pro Energy saving and extremely fast
LXDE is a simple desktop without a lot of bells and whistles, this allows it to remain lightweight which helps conserve battery power and maintain its speed of use.
Pro Simple and straightforward menus
LXDE utilizes a XP like menu which is straightforward and familiar to many users.
Pro The most lightweight desktop environment
LXDE is by far the most lightweight desktop environment, even topping XFCE.
Pro Nicely balanced between speed, stability and features
Pro Designed for cloud networks
LXDE works well on lower end devices such as cloud computers or netbooks. it is able to do this because of its low CPU and RAM requirement.
Pro You can setup LXDE with the same look across different machines easily
Most of the configuration of LXDE is read from files. Consequently, you can store and manage these files in the same way you might manage other dotfiles, meaning that you can setup LXDE to your liking on a new machine very quickly and easily.
Con Development has slowed
LXDE is slowly reaching End of Life, but will still receive new updates as long as GTK +2 is in use.
Con No compositor
In order to keep the system light weight and CPU/GPU non intensive LXDE forgoes a compositing program, because of this there will be screen tearing. Though a compositor like Compton can be added for those that want it.
Con Only halfway to GTK+3
Most of Xfce's components were built in GTK+2 and the upgrade process to GTK+3 was very slow due to the lack of manpower.
Con Doesn't look very well out of the box
But it is very customizable.
Con Problem with log in
"The session is locked" message is a frequent problem when working with Lubuntu.