Mike D'Angelo’s review published on Letterboxd:
More than a stunt, but it almost didn't have to be, given how inherently mesmerizing it is to watch a child grow up—for real—within a fictional context. (That was for me the primary appeal of the Harry Potter movies, but seeing it happen annually over eight pictures just doesn't have the same impact. Likewise Antoine Doinel, etc.) For a long time, the title seems wrongheaded, as Mason's parents and sister are equally vivid presences; indeed, I was ready immediately afterward to watch a three-hour companion piece called Girlhood, with Samantha as its focus. Around the time that Coltrane's voice drops, though, he suddenly becomes a fascinating presence in ways that it's hard to believe Linklater could possibly have foreseen. In many ways, Boyhood is like watching incredibly slow time-lapse footage of an insect from the larval stage to the moment it emerges from its chrysalis, except that we also get to peek inside as it metamorphoses. And Linklater wisely opts to focus almost entirely on glancing, offhand moments, which makes his occasional stabs at conventional drama—the abusive drunken stepdad stuff, in particular—seem all the more clumsy and misguided. I might have preferred a more complicated ending, but at the same time that seems like it might amount to a betrayal of the film's shaggy ethos. Plus, it's immensely satisfying to see Linklater come full circle by turning the college-age Mason into somebody who could walk right into Slacker.
(There's also the formal Las Vegas Weekly review.)