My experience- taking 600 for 6 years:
When I first started
- extreme fatigue
- restless legs at night
- eating, eating, and gained up to 50 lbs, after 3 months

Now:
-I do get sleepy at night but not drowsy during the day
- can't lose weight
- am on a pre- diabetes meds (metformin) b/c my became glucose is an issue

Overall:
It's the only med in my cocktail that has worked for my manic states. When I am climbing to a manic state, it only takes one or two doses to get me thinking straight. I'm weaning off it now to trileptal for manic episodes because I can't stand the weight issue.

Good luck. It is worth it in the short term, but takes a little while to get through the symptoms.