The book-to-movie films of the last few months have really reinforced my preference for books over movies. I had high hopes for Marley and Me but the movie was kinda shallow. The benefit of books is that the author is able to express a depth of feeling and a wide arrange of emotions that actors can only "show" in so many ways.
If you haven't read the book but want to see the movie, I recommend seeing the movie first. It's kinda funny in certain parts, but the book is hilarious. The movie is kinda sad at the end, but the book is a tearjerker.
Marley makes my Sofia look like a little brown angel. Marley, as portrayed in the book, is probably the worst case scenario for potential lab owners.
The best actor award for this movie has to go to Dr. McSteamy from Grey's Anatomy as John Grogan's reporter friend. McSteamy's character wasn't in the book at all as far I recall, but that addition to the screenplay made the movie edition better.
High points of the Marley movie: cute dogs and McSteamy.