Doug Dillaman’s review published on Letterboxd :
The basic concept - following five puppies for twenty months to see which of them become guide dogs for the blind - is such a can't miss premise you'd have to work hard to foul it up. And they don't; even with a few standard documentary sins (basically a commercial for Guide Dogs, overemphatic score, pushing dramatic weight farther than the central conceit really carries, and one outcome that I suspect never would have happened if cameras weren't involved) it works. I cried eight times, and most of them were (as one interviewee says) "happy tears". The rest of the time I was mostly smiling. I mean, for fuck's sake. You're watching puppies for 90 minutes. What's not to love?
Also: I've never seen a documentary so seemingly geared to set up a sequel. May I suggest PICK OF THE LITTER 2: PUPGRADE?