I would agree with Daniel - the extent to which it is useful may be dependent a bit on trying it for yourself and seeing how it works for you, or maybe adapting aspects of it into your life in such a way that it might be helpful. I've actually been seeing someone at the mindfulness clinic and have benefitted a lot from the experience - I believe they also offer group sessions. The way I see it is that, through meditation, I can gradually can learn how to "turn off" that worrying voice in my head that always reminds me of the worst outcome, or that deepens or maintains me in a depressive state. As you train yourself to just try to be with yourself and focus on my breath for a few minutes each day (I tend to do it in the subway on my way into work, just find a corner, close my eyes, and breathe) - it helps to at least break the "treadmill" of continual worry I tend to be on, and gives me a bit of time after the end where I come out with a bit of a different perspective than when I started - it helps to calm me down and get me more in the moment.
I was like Paulm - I had tried it a few years ago and it didn't seem to work for me then - but I was in the midst of a pretty deep depression then, and what I've since read is that that's sometimes not the best time to start - you almost don't have the energy to keep it up and just end up feeling worse off about yourself for "failing" at it. It almost helps to start when you may be a little down, but still have energy to accomplish some things or at least to set aside a few minutes each day to start something - a lot of it is just about getting to do it a few times - its not something that comes immediately to many. In fact some meditators who have practiced for years still encounter the intrusive thoughts that a beginner would, its just that, with practice, you get better at not letting a thought that pops in your head totally derail your meditation, you learn to let the thoughts "glance off" you and go back to focusing on the thing you were doing, like your breath.
There are some wonderful youtube videos by a philosopher called Alan Watts which I like as they help to describe a bit of what its like to practice meditation, or why it may be good for you if you are a person who is prone to worry. Here is one example:
https://www.youtube.com/watch?v=emHAoQGoQic - I really like many of his videos, they seem very insightful - he was an early adopter and popularizer in the west of Eastern philosophy like meditation and other topics.
I hope that's helpful. And of course, the main thing is don't get down on yourself for "failure", whether that's not sticking to a particular meditation course or some other lack of continuity - I am slacking after a good start at the meditation, for example - the whole point is just to try and pick up where you left off, and not be too hard on yourself, as that just makes things worse, or doesn't help you get into a meditative state. I'm happy to talk about it more if you like, but I feel like I've rambled on enough here, so I'll stop for now
