Providing a quiet, disruption-free and hygienic environment for employees to sleep in seems like quite the commitment to make. I'm all for it, and can just the same understand why it would not happen in most environments.
I can see how taking a break from the regular grind can help things, but not sure that naps are really the answer. Going to a buddy's office to shoot the breeze, or taking a walk around the block seem equally beneficial.