Clean My House, Please
When I thought about your question, which perk would I like the most, free house cleaning was the first thing that popped into my head, so I was delighted to see that the folks at Evernote have built this into their perks.
I also would LOVE to work at the Epic campus, Treehouses are infinitely cool.
For the most part, though, as you rightly note, a lot of these perks seem designed to appeal to those who never have time to leave the "campus.: That's why I'm most impressed by the companies that are incentivizing workers to take their vacation time. That's a true productivity enhancer that far to many of us (myself included) find too many excuses to overlook. It never seems like the right time to take vacaton time...and even when we do, we never really disconnect.
So in addition to, or even in lieiu of the financail incentive for vacations, it would be nice for companies to figure out how to truly help their employees unplug by having enough staff to truly cover another person's work while they are out of the office.