My favorite part is my evening is wide open for relaxing. I often find it hard to truly relax as my brain nags me saying I should be working on something. But with this system, the guilt goes away.
It's not sustainable though. I tend to do it in chunks and what's going on at my day job also influences whether I'm doing it. I also need to go to bed early to pull this off, which doesn't bother me but might others. The key is to listen to your body and brain and recognize when you need to back off.
I've blogged about this a couple times: http://mattgreer.org/articles/waking-up-at-5am-to-code/ http://mattgreer.org/articles/still-waking-up-at-5am/