My 2560 x 1600 monitor does not have four inputs for four PC's.
Mine does. I've got enough inputs of various formats on my U2711 to connect five inputs (2xDVI, 1xDP, 1xHDMI, 1xVGA), on top of the television inputs (1xComposite, 1xComponent). If you ignore all the analog inputs, you can even use cheap or passive adapters to get from four computers' digital outputs to the monitor's digital input.
This is one of the big flaws with the U2412M. It's one of their midrange monitors, not high-end, so it only has a basic set of inputs (1xVGA, 1xDVI, 1xDP). You couldn't use it, for example, to connect an xbox digitally, because it has no HDMI, and even with an adapter, you'd have no audio (the U2711 decodes HDMI audio to a headphone jack that you can connect to your sound system). -- Developer: Tomato/MLPPP, Linux/MLPPP, etc »fixppp.org
You have a strange idea of what a "big flaw" is! The inability to connect an Xbox to it without an adapter isn't something most people would ever think about. Another thing you can't do with the U2412M is lay it flat and use it as a cutting board, because you'd crack the screen! It is, however, designed to be a computer monitor, and does that job extremely well.