I saw it the weekend it was released, and I really enjoyed it! Visually it was nicely done, and the ending wasn't changed in its tone from the book or 1974 movie (the David Suchet one altered that a bit).
The 1974 movie is still my favorite, but this one is just under it, followed by the David Suchet one from a few years ago, and I've erased the horrible TV movie with Alfred Molina from my memory forever.
Part of why I like this movie is the care the Branagh put into it, having a train built, trying to keep true to a Christie style, etc.
My technical nit was the smoke deflectors being reversed on the locomotive! But the visuals with the train (expecially travelling through the snowy landscape) were beautiful to me.