I guess I have three questions about it (and of course about most herbs)--
little scientific study--what there is is promising with moderate depression (might have fewer side effects), but still, there's the example of kava kava that everyone was promoting and now it turns out to possibly cause bad liver damage (at least in some)
no regulation, so no idea what you're getting. some things I don't mind, but I wouldn't want to add a roller coaster to my depression from the fact there's no quality control
st. john's wort interacts badly with a lot of prescription drugs--causing a lot less to be absorbed. So, if you're taking anything else, I'd be very wary.
Some day it might be a great choice, right now--espeically with lily and kim's bad experience, I think I'd try a different approach.
The most consistently effective approach to depression is intensive exercise (intensive for you that is). It has an immediate effect, only good "side effects", and is as effective as prescription drugs.
I take a prescription drug, but it was a long hunt and you want help right away.