I recently purchased a U2713HM from Amazon, and it has been having issues playing well with my PC when using the DisplayPort connection. The other connections don't have the same issue, but also don't support the full resolution, which is an issue in itself.
My current setup is a Clevo P170EM laptop with Intel HD 4000 integrated graphics and a Radeon 7970M hooked up to the monitor via DisplayPort (on both ends, no adapters). The monitor is detected, and I can interact with it properly through the Control Panel and through the Dell Monitor Utility. However, the screen will often go black without warning and stay that way until I unplug and replug the DisplayPort cable. The monitor still has power (the power LED is on, at least), but the monitor is blank, save for a "Entering power saving mode" notification.
The most peculiar part of this is the fact that the monitor works fine with my MacBook, hooked up via a MiniDP-DP cable. This points to my laptop as the likely offender, but I have used it with many other external monitors just fine.
A final note: the monitor seems like it goes blank shortly after there are graphics being drawn to the monitor. If I leave all of my windows/applications off of the monitor (onto my laptop screen), it seems to not go blank quite as quickly.