It's rather interesting that so much mental stimulation can come out of insomnia.
I recently had a side job doing technical editing for a technology book. It involved lots of reading. My wife works evenings and we have a toddler so my time after work is consumed by him so I wasn't able to do much work on my reviewing until after 8 pm most nights. As a result I struggled to finish the evening's block of work to me nightly fatigue. However, after I finished, I'd check email and get distracted by something that would lead to continually cascading diversions until before I knew it, the little hand on the clock had worked it's way past 1. There I'd be more awake then when I put my son to bed almost 5 hours prior. Of course, the very fact I stayed up too late would be the source of the next evening's difficulties. Oh the vicious cycle.
At the moment it's almost 3:30 AM. I went to bed early quite tired and with a headache. I think I slept for a few hours, then awoke for my nightly fight with the cat over my claim of the bed. This was followed by an hour+ of tossing and turning as I thought about work and side projects, other miscellaneous distractions and my resurfacing headache. After a while I gave up, took some pills and came to the computer. I have since spent about 30 seconds checking email and several hours writing blog posts and looking up random word definitions on google.
I wish I had a hibernate button.