I saw this movie last week....and I LOVED IT!
Yes, it's a tear jerker......but fortunately it only becomes sad for the last 20 minutes or so. The majority of the movie shows the story of how the dog and man came to meet, and the relationship they shared.
Definitely a movie to watch if you love dogs, or animals in general.......keep tissues ready for last 20 minutes, but this movie is TRULY wonderful!