To change the fan settings, simply tap the button. There are three settings for the fan: high, low, and off. By pressing and holding the button, you can change the units that the temperature is presented in.
I tested the effectiveness of the fan by leaving it in each of the three settings for 24 hours, and then collecting the final temperature at the end. When the fan was left in the hi setting, the temperature was fairly stable at 27C. The low setting yielded a temperature of 29-30C, while leaving the fan off quickly allowed the temperature to skyrocket to 39C. Needless to say, the fan is very effective at keeping the drive cool. The fan wasn't very loud in either setting, but when it was left in hi it did give off a slightly unpleasant high pitch whine. Unless your sleeping in the same room with it, leaving it set to high shouldn't pose a problem.
I didn't like the fact that when you shut off the computer the Vortex always defaulted back to its factory settings, which is the fan being off and temperature being expressed in Centigrade. So you have to remember to turn on the fan after you start the computer. I really don't mind the fact that it can't remember its last settings, but it would be nice if the default setting was for the fan to be on. Other than that, I couldn't find anything major that I didn't like or would change.
You can pick one up at the fine folks at CrazyPC.com.