Higher static air pressure

The FX84XW has one of the highest static air pressure ratings you can find, by 3-5 times. This means that when you are dealing with small spaces or lots of cables, this fan can push air around them instead of cavitating. Many average fans won't push air if there's much of anything blocking the exit path of the air. The FX84XW does a better job at pushing the air through and this is a very useful fan quality for small cases.

Manual Speed Control

Some may like this others may not. For the over clockers, people who want to be able to force a fan speed, or for those that want to control the noise level this is very nice. You have full control over the fan. You don't have to worry about a thermal sensor not working right and letting your system get to hot or getting too noisy at your favorite part of the movie.

I found that the first fifth and the last fifth of the speed range made no effect, but in between that it was very accurate and very controllable. The speed was constant and never jumped up or down.

The wires that connect to the fan from the speed controller are very long, almost 4 feet. The cable wires are thin so it's easy to tie up the excess.