I'm going to let the trailer speak for itself.
The plot of The Tree of Life is still something of a mystery. Though I'm not sure if it even matters. Terrence Malick's films are generally not about story or characters, but about exploring ideas and feelings through images and dialogue. As films, I'm not sure they always work. As lyrical explorations of tone, I think they work magnificently.
My prediction is that this will, like all of Malick's other films, become a cult hit critically while colossally failing commercially. Only when film criticism catches up with Malick's current crop of films (This, The New World, The Thin Red Line) like it did with his first films (Days of Heaven, Badlands) do I expect Malick to get the recognition (and acclaim) that he deserves.