For the most part, I like Terrence Malick's loose and experimental style, but The Tree of Life is confusing to the point that is mostly rendered ineffective: the director's decision to cover so much ground, with a story that spans the Earth's inception to our present day, is admirable, but ultimately the meandering and purposely ambiguous nature of the picture does The Tree of Life a disservice. The film loses much of its meaning in its decision to impress us with its scope and visual splendor.
There are some, of course, who might argue that The Tree of Life is confusing because that's the way it's supposed to be, but I'd argue that Malick's point would have been better made had he not resorted to the story's freewheeling, throw caution to the wind, purposely "about nothing and everything at the same time" narrative structure, which borders on the pretentious (hell, it crashes on the pretentious). Malick is aiming for the great heights of 2001: A Space Odyssey, of course, though his film provokes discussion and interpretation for all wrong reasons.
With Kubrick's movie, we were baffled because we were awed. Here, we're baffled on account of being simply confused.