The one time I used it over a few weeks was a generic brand. The on-label effect worked, but I had one disturbing side effect: terrible nightmares.
Unscientific conclusion, but the nights I took it when with my new gf at the time, nightmares followed. Binned the remaining pills, nightmares vanished. Possibly the generic additives factor, or maybe the drug itself. Who knows, never tried it again after that.