I have heard some people having luck with Synergy.
Synergy is Free and Open Source Software that lets you easily share your mouse and keyboard between multiple computers, where each computer has its own display. No special hardware is required, all you need is a local area network. Synergy is supported on Windows, Mac OS X and Linux. Redirecting the mouse and keyboard is as simple as moving the mouse off the edge of your screen. Synergy is released under the GNU Public License (GPL).
I should have specified, as RedGrittyBrick has said, Dual Monitor KVMs exist.
If the price is a bit much for you (there are some budget ones, but, they can be pricey) Also consider getting 2x normal KVMs and use one just for the screens (Make sure they are powered, or at least the second one is, as some key power from the keyboard/USB port)... I think you just had a bad experience, I have even seen some cheap ones (<£10) from eBay being very good.