OK, let's say you've looked at every other desktop environment, and your reaction to all of them can be summed up as "ick!" "Why does everything have to be so primitive?", you ask, "Doesn't anybody care about the quality of the user experience any more?" You are tired of all this blather about simplicity - you want a full theatrical multimedia showcase that blows you out of your chair!
Enlightenment is the Las Vegas Boulevard of desktop environments. When a user expresses dissatisfaction with Enlightenment, the developers are crushed; they flagellate themselves with cat 'o nine-tails and wail "The User was not Impressed! We must work harder!" Enlightenment knocks itself out to be the best-looking desktop environment anywhere. It comes with a full suite of custom-made programs which focus solely on the user experience.
Features? You didn't know the meaning of the word features until you've found Enlightenment! Desktop rain and flames! Dancing icons! Transparent everything! Themes that can make it look like anything from a pirate ship to the bridge of the Starship Enterprise! Take all of the endlessly excessive gaudy double-chromed whistles, bells, gongs, horns, drums, kazoos, and dancing elephants you've ever seen in your life and put them on one desktop: that's Enlightenment.
Enlightenment is surprisingly fast for all of the special effects it's towing, but even at that it's speed is somewhere between KDE and Gnome; not the swiftest desktop you've ever run, in other words.
Enlightenment has a few handicaps. Because it's programs are so woven together with the environment, you typically have to be running the whole desktop to use an Enlightenment program. Like Gnome needing GTK and KDE needing Qt, Enlightenment needs it's own library suite to run. Enlightenment is strangely hard to find; I only know of one distro that has Enlightenment as it's default desktop, and that is the Elive CD Installing Enlightenment on another distro may range from difficult to impossible.
Another difficulty is that Enlightenment re-invents itself with each release, so there's also very little compatibility between versions. Themes for one might have problems with another, for instance.
Also, there is an issue with consistency. Each Enlightenment program has it's unique ways of doing things - interface included. Even more gravely troubling, your choice of theme can change the entire desktop's interface. Since Enlightenment is designed so that you can customize everything including the controls on windows and menus, this is exactly what every theme developer does. So, depending on which theme, you may have to close a window by clicking on the bottom-right corner in one case, or clicking a button in a menu attached to the left side of the window in another case, or by picking it off a pull-down menu from the top right corner in another case...and so on. Customizing your own environment can be challenging, and theme design is impossible for all but the most geeky. If you fiddle with it too much, it's easy to break it and not know how to fix it.
Make no mistake, I actually like Enlightenment! All of the problems I have listed here are simply inherent in the process of being so sophisticated. They are dealt with by the development team in a heroic manner. Everywhere possible, Enlightenment leads you by the hand. Every effort has been made to create an immersive user experience, not just in eye-candy, but in usability.
If you haven't guessed by now, I would not recommend Enlightenment for anybody who uses the computer for serious work. If, however, you're all about leisure time, if your primary purpose in life is to make your friends burn with envy at your stylish desktop, then Enlightenment is for you!