Je pense que...
It depends on if you mean psychiatrist (medical doctor with additional training in diagnosing and treating mental illness, i.e. can prescribe meds), or psychologist (a non-medical specialist in the diagnosis and treatment of mental and emotional problems, and thus no meds). There seems to be some question on which, psychiatrist or psychologist, you are referring to in your question. Suppose I'll respond for both...
I do not mean to offend anyone. I am going to generalize. :/
Psychologist: One of the most popular majors, next to communications, is psychology. And thus, many who practice it, are, say, under-qualified. Still, if you just need someone to talk to, someone who can look at your situation without bias and who you can trust on a professional level, then a psychologist is very helpful. They're perfect for verbally unloading all your stress, and they make you think and suchlike. (Isn't it interesting that many psychologists see other psychologists... :-)) Anyways, I don't particularly like them, but I do not particularly dislike them either. On the whole, I'd say all you should pay them for, and expect from them, is a good ear and thought-provoking comments on your life.
Psychiatrist: Tricky, tricky. I do not have much trust in them, only because they have the power to divvy-up meds, and often do not do so correctly. I understand why medicine is so helpful, chemical imbalances, mood control, etc., but I am horrified by the misdiagnoses. I mean, a close friend of mine has been to several, and they have all misdiagnosed and thus severely upset her, not to mention driven her pathology to new heights. More frightening than this, is what is going on inside her mind,(forgive my lack of a better way to put it), is rather simple to diagnose: me madre, I, and madre's psychiatrist-friend all agree. Still, this friend of mine has been to at least 6 and they have... failed to do what is necessary. Anyway, I think psychiatrists are just as likely to fail as psychologists, except that if you see a psychiatrist, you must be wary of what they put you on.