I've done a 6 and 2 biphasic schedule (or sometimes 7 and 3), and I felt better than I ever had before. It's difficult to fit the nap in with work though.
I think in many ways the "Italian" sleep schedule (up at 7, awake till 2, sleep till 5, awake till 2) is very natural. It's no less sleep, but it feels more refreshing somehow.
Depending on where you live, the hottest hours of the day are usually between 12 - 5. Maybe it's instinctual for predators to not want to do stuff during those hours?
I think in many ways the "Italian" sleep schedule (up at 7, awake till 2, sleep till 5, awake till 2) is very natural. It's no less sleep, but it feels more refreshing somehow.