An independent study was just released showing that antidepressants really aren't any more effective than placebos. (Read more about these findings here.) I'm not surprised; pretty much anyone I've known personally who has been on these drugs doesn't seem to get any better, they just kind of stay the same, at best.
But I do think the drugs do something to your brain, which is probably why people feel like they are getting their money's worth. I've tried antidepressants a long time ago; I can't use them because I'm allergic (as in I could have a seizure). I've also tried St. John's Wort a handful of times (which was probably a bad idea considering I'm seizure prone), and my brain always felt a bit "funny" on it. But does a temporary increase in seratonin really cure depression in the long run? Umm, apparently not.