Works fine. My 30NF is plugged into a PCI-E Geforce 7900GT (which came with a molex>6pin PCI-E adpator). You can buy adaptors from shops for about $2 if the graphics card doesn't come bundled with one. Bear in mind also though that the 30NF comes with a 20pin plug, so if you have a modern motherboard eg. NF4 rather than NF2, you'll also need a 20pin>24pin power adaptor plug. Again, about $4 from an electronics store. Here's the Silverstone version (though any brand will do):
BTW, I've been running the 30NF practically 24/7 for last 12-18months now and its been superb, and rock solid stable. Fabulous piece of kit.
The only unsuitable systems would be SLI systems with 2 x high powered graphics cards because I suspect that 18A on the 12v rail won't be enough.