Pros: Among the best formulations on the market in the USA, particularly Nature's Way Perika.
Cons: St John's Wort isn't for everyone -- do your research.
St. John's Wort is an herb that's been used for hundreds (or even thousands) of years for many different purposes (mood elevation being one of the primary uses). It's prescribed regularly by doctors in Germany and other European countries for depression, the same way Prozac and such are prescribed here in the U.S. It can also be helpful (anecdotally) for anxiety/panic, fibromyalgia and certain types of pain, as well as having an antiviral effect. There are a number of clinical studies showing it's efficacy for mild to moderate depression, but there's a debate as to whether it works for major (clinical) depression -- a large study was done in the USA showing it doesn't help for severe depression, but there's still some controversy surrounding the conclusions.
Nature's Way sells several variations of St. John's Wort. There's a "regular" Nature's Way SJW product, Nature's Way Standardized Extract, and Nature's Way Perika (which is a product made in Germany where SJW is commonly prescribed, proven high in Hyperforin which is the main active ingredient, and using a special system called HyperiSure which is supposed to guarantee the stability and potency of the active ingredients).
I've been taking St John's Wort for about 2 weeks now (300mg 3x/day with or without food -- doesn't upset my stomach either way), and have experienced a noticeable improvement in my moods, as well as reduction in anxiety (I also take clonazepam, and have been able to reduce my dosage of this benzodiazepine by almost half). I started with a bottle of Natrol brand, but after hearing numerous positive anecdotes I purchased a bottle of Nature's Way Perika, as well as a bottle of Nature's Way Standardized Extract.
Nature's Way Perika has some of the best anecdotal reports of efficacy of any brand of St John's Wort on the market. I highly recommend this formulation. I also recommend Nature's Way Standardized Extract (the bottle specifically says "Standardized" in large letters on the front), which received an excellent lab test review from Vitacost (dot com). I would recommend these two formulations, but not the "regular" Nature's Way formula. The latter has not been well tested, and I've heard little or no anecdotal evidence that it works well. However, it's worth a try if that's all you can find.
I've used and trusted Nature's Way products for a long time, and their St John's Wort products are among the best available in the USA. Since formulations, dosages and efficacy varies so widely from brand to brand here in the USA, why take chances? Go for Nature's Way Standardized or Nature's Way Perika, and you can be pretty well assured you're getting a potent product that will work for you (provided it does work for you... it isn't for everyone).
I suggest you do some research on the Net (and maybe elsewhere) before starting on St John's Wort. It's more than an herb, it's a drug -- and all drugs can have side effects, as well as interactions with other medications. However, SJW is well known to have less side effects than SSRI antidepressants like Prozac and Paxil, and there's no known withdrawal syndrome from stopping suddenly. As far as I know, nobody has ever been documented to have died from an overdose or other food/drug interaction. It's a pretty safe product, and the fact that the FDA doesn't regulate it as a drug in the U.S. is fairly good indication of this. There's something to be said for the fact that it's been used (and its benefits enjoyed) for centuries all over the world, whereas these Prozac-type meds have only been around for a few decades at best and can have some pretty ugly side effects. Check out this (noncommercial) website and forum for plenty of good info: www.sjwinfo.org .