The Silent-Pipe II 7600 GT from Gigabyte taught us a few things about passively-cooled video cards. Mainly, we learned that silent doesn't mean low performance. Indeed, the Gigabyte 7600 GT Silent-Pipe II consistently proved better than a standard active fan cooler in every scenario, and kudos to Gigabyte for engineering that.
We also learned that the choice of PC case will have a sizable bearing on the performance of a passively-cooled video card like the Silent-Pipe II. Specifically, with this card you'd want a case with no extra grilles for air movement, as topsy-turvy as that seems. The Silent-Pipe II works best when air is pulled from the back of the case to cool the card and is then expelled higher up after it passes the video card, without any extra unwanted turbulence.
The card's primary feature is silent operation, but this selling point also hinge on what kind of system you have. If you have a quiet media center PC with a fan-cooled video card that you want to quiet down, the Silent-Pipe II will do an excellent job making your machine even quieter. However, if you have a loud and obnoxious rig, the Silent-Pipe II will make a much smaller difference.
If you're a heavy PC user, you probably run your machine into the wee hours of the morning, especially if you're into downloading large files. Wouldn't it be nice to finally shut the noise off? Even if your current case is loud, a silent video card is a great start to quieting it down. Invest in some silent case fans and a quiet CPU cooler after that, and you can not only have your high performance, but you can sleep well while doing it.
The Gigabyte 7600 GT with Silent-Pipe II Technology retails for approximately $150 to $180, and a quick check in some online stores in North America shows it's no more expensive than typical actively-cooled 7600 GTs. And after living with the Gigabyte card for a bit, I can't think of a single reason why someone would invest in a noisy video card over a silent one.