HA!
I just ordered pair of these from Amazon last week for my gtx 480's and today I submitted a refund request.
If you're using your card with the stock fan settings, then this cooler may show an improvement. But I use MSI Afterburner (which is free) to control my card's stock fan speed as the temps go up.
Using Afterburner I can keep my cards cooler with the stock fans. The Zal fan's won't spin up fast enough.
Running Crysis, setting maxed, res at 2560 X 1600, and fps ~50, the stock fan keeps the cards right around 75c. With the Zal's on, same settings, I quit playing when the cards hit 85c. It was quite apparent that stock was better.
Also the Zal will take up 2 slots on it's own. Meaning with stock fans my 480 takes up 2 slots and with the Zal it takes up 3 slots.
So, hands down, I'd recommend Afterburner which is free to these $75 fans.