The primary design feature of Fractal's Adjust 108 is the lack of design. The brushed aluminum face is only broken up by vertical grooves for the simple black rubberized sliders to ride on. The white lines give a simple and clean contrast to the sliders that matches the neat Fractal Design insignia.
The small notches below the sliders are for the bi-color LEDs, which may be toggled in intensity between 100%, 50%, and OFF with an LED jumper. The narrow notches help diffuse the LEDs and prevent them from being overbearing like the LEDs on many computer accessories can be. The LEDs are meant to be a subtle splash of color without being overbearing, and Fractal has accomplished that.
The PCB and cable bundles are actually surprisingly neat. It's often tricky business to keep all of the cables tidy in the back of a fan controller, but having the bottom of the controller chassis gives you somewhere to bundle up the cables that aren't being used (if you choose not to disconnect them) or to pick up any slack on shorter cable runs. Many other fan controllers only have cantilevered sides to attach to the drive bay, which often leaves you with hanging, untidy cables. Also each fan port is separated by the sliders on the PCB which makes them much easier to connect and disconnect than when they're all next to each other. Although not all that uncommon, it's definitely nice that the cables are removable.
The fan cable headers are compatible with 4-pin fans but only have three wires, because there is no RPM readout on the fan controller. Power is delivered by a split Molex / SATA power cable, so you shouldn't have any troubles getting power to the Adjust 108.
Installation is simple and fairly self-explanatory, and since there's a bottom to the controller tray, it seats much more firmly into the drive bay which I also noticed help deliver a more secure, flush fit with the front face of our Define XL case. The relatively-flat sliders also mean you won't have trouble fitting the Adjust 108 onto cases with a flush front door, again something we've run into with our Define XL.
The LEDs dish out a little splash of color out of the small bottom slits in the front face of the fan controller. When the slider is above 50%, the LED goes "cool" with a blue LED. If it's in the lower 50%, it shows a white. You should be happy to note these are well-diffused and don't have that blinding intensity that blue computer LEDs are prone to having.