I have suffered from insomnia also. Before having the Mirena I would occasionally have a night where I was awake for one or two hours in the middle of the night.
Lately it has been two to three nights a week where I'll be up for 3/4 hours a night. It's very exhausting when you have three little ones to look after. The other nights I still feel like I'm a restless sleeper, not really getting a solid nights sleep.
I'm getting Mirena out today so will be interesting to see how it affects my sleeping patterns.