I used to take it, and other aminos, years ago. I liked it... but during the past two years most supplements, even multivitamins, seem to aggravate my condition. L-phenylalanine (or however you spell it) and L-Tyrosine were others that seemed to help with the head. I was always cautious about taking too much for too long of a time, etc.--protein balance.
As a matter of fact, before I had this Graves' thing, Niacin--B3--used to be a REAL help to me.