Many people have never heard of clarity enhanced diamonds, so a little tutorial is in order.

Diamonds are classified by several factors, but the most common are clarity, shape, size (in carats) and cut. With speaks to the ease with which light moves unimpeded through the body of the diamond.
What can impede light? Flaws in the otherwise perfect crystallines structure. Like scratches on a glasses lens or smudges on a mirror, each flaw scatters the light and makes for a cloudy, less clear diamond.

Diamond clarity is rated by the number and visibility of the flaws found in the stone. This ranges from flaws that can be seen without magnification.
Many flaws can only be seen with a microscope, and then only by a trained eye, yet still detract from the value of the stone.

Some flaws are surface defects, tiny white or black specs and minute fractures on the surface of the diamond.
Others are caused by inclusions, small defects within the diamond where the structure failed to mature properly or other structures began to form inside.

So what are clarity enhanced diamonds?
These are diamonds with specific defects (or flaws)
which have been corrected or masked by special treatments after the diamond has been cut.

Surface fractures can be filled with a chemical compound, much as you would fill a crack in a wall with putty. This treatment is effective but temporary, and will eventually discolor and wear away.
You can detect a fracture filled diamond by looking closely at the surface. The filled spot will have slight a slight color difference relative to the surrounding crystal, as it interrupts the uniform effect of the diamond on the light passing through. Also, microscopic air bubbles are sometimes trapped in the filling compound, which can be seen with a good glass.

Laser drills are used to excise the inclusions which can cloud up the interior of the diamond. They can be detected by looking for the tiny hole drilled through the diamond to get at the flaw. These tunnels can best be seen from a side view.

Are clarity enhanced diamonds worth the trouble?
It depends on what you want. To the naked, untrained eye, it is as attractive as it's flawless counterpart. Since the larger the stone, the more common the flaws, a process to correct imperfections will allow you to retain the brilliance and clarity of smaller stones with a larger piece.