Ask YC: How many hours do you sleep on average ? 18 years ago
I actually tried polyphasic sleep for a while (6-7 weeks), and it was great after I adjusted. It was a little creepy being up all night, but I wrote a lot of code, and felt fine.
The only problem is the nap schedule makes it impossible to have any scheduled commitments. As soon as school started, I just couldn't keep up with the naps.
My advice: polyphasic sleep is great, IF you don't have any scheduled time commitments.
(If you're curious about polyphasic sleep, I suggest you try it. It's an interesting experience, regardless of whether or not it's practical.)