I know it's hard to adapt a book into a screenplay; some things have to go by the wayside. Reviews here seem to fall into two camps: people who haven't read the book loved it for the most part, and people who have read the book either actively dislike it or think it's fine to give it a couple hours of your time. I think it's fine to give it a couple of hours of your time, but if you read the book, know it will come up short. In the movie, Joe's backstory was basically mentioned in passing through exposition, when really that was a huge part of the book and could have been made really compelling by showing, not just telling. There was too much Joyce time, too much time spent on coaches staring off into the distance at the boats...even when they were standing at the starting line and couldn't possibly actually see the boats after a short time.
I do think the races, few as they included of them, were pretty well done. A lot of people complimented the cinematography, but I thought there were some questionable choices made. Rowing is a beautiful sport, and I don't think they always captured it fully. Props to the actors for their well-done performances.
So bottom line, a pleasant movie worth the time, but if you want depth, read the book.