I've used the original Vantec Nexus, the Sunbeam, the Zalman, and the Super Flower. The Super Flower is in my system now, and has been for a while. I feel no need to replace it.
The Vantec made a buzzing or humming noise due to its voltage regulation methods. That drove me nuts. Also, you can only drop the voltage to 7V. After that, I specifically looked for controllers that didn't use that method.
The Sunbeam was next up. That lasted maybe half a day. It looks tacky with its ultra bright LEDs up front. The abolity to turn off the fans is completely useless to me. The actual usable area of the dial (let's say between 5 and 12 volts) is parhaps 1/8 of a turn. The rest does those useless voltages. And really, do you want the ability to turn off your CPU fan? It uses these large ghetto-looking heatsinks which are really just bent metal sheets.
Then came the Zalman. The knobs are flimsy on it. Otherwise it's not bad. The blue color probably won't match your case. The LEDs only light when there is a fan with speed cable is connected. This means all my Panaflos did not make the front panel light up. When you do find a fan that makes it light up, turning down the voltage makes the LED blink rapidly. I don't find that desireable. The two switches probably won't get used on it. You need to bare the wires of whatever you're going to connect to them. The aluminum mounting brackets are very easy to bend, and don't do the best job securing it to your case. The Zalman only allows from 5V to 11V. I don't know what that extra volt is going to do. I've moved that unit to another PC, and its first channel failed while a the CPU fan was connected to it. Take that for what it's worth.
And now I've got the Fan Master by Super Flower. The display is easy to read, and you cange the colors on it. The face plat swaps out, but I haven't tried that. My controller was missing the wrench and thermal tape it's supposed to come it. The brushed metal matches my Lian Li, so I left it. It seems to have similar construction to the Zalman as far as the components go. The knobs are fine. You can set alarms for fan failure and temperature. It has four temp sensors.
If I were looking now, I'd check out the Cooler Master Aerogate 1, but its high price would deter me no doubt. Really I can't think of any other reasonably priced rheobus that can do as much as the Fan Master while still seeming to be quality-made.