Remember to watch the director's cut ending! It will crush you, no doubt, but it elevates this movie to a whole other level. The other endings don't match the tone of the movie and just pale in comparison.
Movie-wise, with countless plot-holes and stupid lines of dialogue, The Butterfly Effect is not a 4 star movie. But, that's where the emotional impact of this movie steps in. Movies are supposed to make you feel, and this one certainly achieves that.
The acting is good, but nothing extraordinary. The movie looks okay and as I already mentioned, the script is stupid at times. However, the base idea behind the story is just wonderful and immensely powerful. Some scenes really manage to shake you to the core.
It took me long enough to watch this, and luckily, I approve of its existence.