I agree with what's been said so far. Dreams can be cool and can add a lot to a story when used right. I think, like most scenes, they just need to have a purpose, whether they're foreshadowing something, expressing some hidden feelings, hinting at some back story, or whatever. Sometimes the deep, cryptic ones can get kind of confusing to read, which is why I don't think they should be overused, but dreams ARE confusing, and I think it's okay to write in a dream that isn't totally spelled out for the readers, as long as it adds something - even if it's just a sense of suspense and uncertainty.
I went through a big dream phase when I was writing Broken - I was really into dream interpretation and creating these dreams that would foreshadow in sort of symbolic way. Then I got over that phase, and now I'm not big on the dreams anymore, but they can still be cool sometimes.