My older two boys share a room and sleep in bunk beds. Since we moved them to bunk beds it's been great as it has opened up a ton of space in their room for quiet time away from the chaos of the rest of the house. I love bunk beds.
TreeHugger has shown many ways to hide the bed; most are designed to gain more space. But the Red Nest by Paul Coudamay doesn't; the bed is still there taking up space, but is hidden by the sliding bookcase.