I work as a self employed game developer and favour a 32 hour day sleep cycle, this allows an hour when I wake up and an hour before I go to bed to relax, I then work for approximately 20 hours with regular breaks and sleep between 8-10 hours. I do this for 3-4 cycles and then take 2 cycles off from working.
This is obviously very awkward when dealing with meetings or anything in the 'outside world' but I'm rewarded with huge amounts of free time and loads of time to get work done (which I greatly enjoy doing).
The only real issue is that everyone else on the planet works on a 24hr day sleep cycle so it's a nightmare arranging things or committing to regular weekly schedules at set times.
I've been using a 32 hour cycle for about 7months, it took around 3 weeks (on the 24 hour calandar) to adapt to this sleep cycle, the main issue is adapting a 32 hour day to a 24hour day calandar but once your body is adjusted your cycle stays at 32hours but you'll continue to abide by the 24 hour day calandar as a reference to the day/time.
If you're lifestyle permits it, I would recommend giving it a go. It's a little bit like magic, one day your complaining there's not enough hours in the week then after adapting to the 32 hour cycle it's like you suddenly have all the time in the world!
Again, not for everyone...