What would otherwise be a pretty good, if old-fashioned, melodrama is made memorable by a climax that still holds up decades later as one of the most exciting scenes on film. The movie as a whole is imperfect - it's a bit too long, and is occasionally preachy - but it fits together well, and is a deserving classic of the silent film era.
The story is openly moralistic, and would not have worked without good characters and acting. Lillian Gish is deservedly remembered for her role, but Lowell Sherman is also important as the oily Sanderson - his understated performance makes his villainy more effective, and balances out the parts of the movie that are more heavy-handed (the title cards, in particular, leave no doubt as to how the director feels). The story ends up working pretty well in the context of its era.
What really stands out, of course, is its terrific climax on the river, still justifiably praised after all these years. Carefully conceived and beautifully photographed, it is a most effective way to wind up the story. The riveting drama and the stark beauty of the scenery make a great combination that you won't forget.
This would have been even better if it had been maybe 30 minutes shorter. Some scenes go on longer than necessary, and there is a lot of filler material about the townspeople - mildly amusing, and comic relief from a heavy story, but the comedy is not exactly of Buster Keaton or Charlie Chaplin quality, and a bit less would have been better. Still, the majority of the time the film does keep your attention.
"Way Down East" is a classic in spite of its flaws, one that every silent film fan will want to see. And it also would be worth watching for the climactic sequence alone, for anyone who appreciates quality cinema.