You have to wonder, if the Wii creates sufficient heat to warrant an additional cooling fan? Especially considering that the Wii, is next gen in all areas but the labour intensive graphics, ie, the chips that create most of the heat are only a step on from the Gamecube processors...
Before I brought, and i've had this for some time now, i was able to check the temperature after 1 hour's play in a graphically intense game, Res Evil 4. Internally my Wii was venting air at 40degrees centigrade. (thats pretty hot)
WITH this system turned on, my Wii vents air at around 8degrees less dependent on ambiant temperature. (enclose your Wii in a TV cabinet with limited space and air flow and you are asking for trouble).
The Only annoyances are....1 for such a tiny fan, it's noisey. I had to dismantle mine and reseat the fan with a felt pad. 2, the blue lights are bright and distracting, and they don't turn off when you power down into standby...which wouldn't be hard to integrate.
Overall if your Wii is gasping or Freezing Mid Screen...buy one...it's worth the time and money.