I'll add my experience, mostly because it highlighted a side effect rarely mentioned, which I feel should be.
I was at a really low point and started taking it to try and help level me out. I'd say it started to work. I had it in a capsule form and was nearing the end of the bottle and trying to decide whether to get another. I actually wrote about it on here and thankfully Ligayagardener, who was still on at the time, saw it and warned me that it could be an issue with my complection, being a redhead and pale skinned, he meant.
I'd actually been having tender skin and the slightest scratch was painful, almost like sunburn, except I wasn't sunburnt and the pain was lasting longer. When I looked into it, it turned out that it makes you sensitive to sunlight and at this point I realised that it was just the areas exposed to sun that were experiencing this, namely the backs of my hands, my arms and the tops of my feet exposed by my sandals.
So a warning there for fair skinned people. It took a couple of weeks after stopping taking it for my skin to return to normal. I surprised it's not mentioned more often in the cautions on it. Usually it's just the drug interactions that are highlighted.
My alternative is rosemary. It's not as efficient, but no side effects for me.