I briefly tried an arrangement like this, which has just one surface for both keyboard and monitor. It worked horribly for me, though perhaps I am odd.
It works much better to have the keyboard at a good keyboard height, and monitors at a good monitor height. I've built a couple variations over time, see my 2010 version partway down this page:
It works much better to have the keyboard at a good keyboard height, and monitors at a good monitor height. I've built a couple variations over time, see my 2010 version partway down this page:
http://kylecordes.com/2010/standing-desk