We've been waiting a few months for the Mini DisplayPort to Dual-Link DVI adaptor in order to hook up our 30-inch Dell 3007WFP monitor, but when it got here, it was periodically unusable.
Here's the issue: occasionally (somewhere between a few minutes and an hour), the screen will look like it's missing half its display information, like one of its dual "links" has failed. This can only be fixed by unplugging and plugging in ether the Mini DisplayPort connector to our MacBook Pro, or the USB connection (yes, the adaptor uses both DisplayPort AND USB).
And this issue doesn't seem to be isolated to Dell's displays, users have the same screen distortion with Apple's 30-inch Cinema Displays as well.
Our own limited testing showed that this happens really quickly (in about a minute) when there's a USB hub plugged either into the second MacBook Pro USB port, or into the pass-through port on the actual adaptor itself. If we have nothing plugged in, the display is fine, but if we have a powered hub plugged in, the distortion hits almost immediately.
Here's hoping this is an easy software fix. And, we probably just found the reason why the adaptor was delayed so long. If you're looking to buy one of these, hold off until the problem has been fixed.