I too suffered from insomnia since the age of 5, (29 now) and I've been on 140mg/day MMT for 1.5 years now after 11 years of oxy/heroin addiction and I sleep better than I ever have before. I'm tired at night and fall asleep as soon as my head hits the pillow.
Sure, some nights I'm not very tired, but even then, if I lay down eyes closed in a dark room, I'm asleep in 30 minutes which is incredible for a true insomniac. Mind you, at the time I got on methadone, I was doing 1,200mgs of oxy per day (80mg OP x 15 per day) or 40-50 bags of nyc dope per day when no oxy was around so its not as if my opi tolerance is why I'm sleeping so well on the 'done...its just a groggy, sedating ass chemical.
HOWEVER, I'd suggest getting on Bupe/suboxone instead. I'd been ddicted to opi's for bout 8 years when I went on bupe, and it was great. It didn't make me groggy at all, but I felt normal which was what I wanted. I got injured, had to go on painkillers, relapsed, ended back up on oxy/dope for a while, then had to go on 'done b/c couldn't afford to detox from the OP's before starting the bupe, but I wish I had. I'd rather be on bupe any day of the week. Sure 'done let's me sleep at night, but I'm also falling asleep during the day from the stuff. On bupe I'd be fully functional, and just smoked some pot to sleep at night. Now I'm tethered to the stuff..
Just mt 0.02, good luck either way