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.
Simple and straightforward menus
LXDE utilizes a XP like menu which is straightforward and familiar to many users.
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 requirements.
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.
Development has slowed
LXDE is slowly reaching End of Life, but will still receive new updates as long as GTK +2 is in use.
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.