I liked it.
It's a movie about Matt and Abby in a dead relationship. The relationship has probably been dead for some time but neither of them knows it because they don't talk to each other about their feelings and desires. The relationship felt real, like a couple of people who have never really been with anyone else and who fell into a lot of bad habits with each other in the early days of their love. I thought the sleepwalking would somehow be important to the plot, but it acts mostly as a framing metaphor. Which is: Matt (and Abby, too) sleepwalks through his relationship, avoiding the questions that occupy his mind (how do we/when do we/should we get married?). Matt's emotions, which he doesn't understand and can't control and doesn't know how to talk about, drive him to do things that are strange to him. When he ignores his sleepwalking, he's nearly killed (a couple of times!). When he ignores his feelings, he almost marries Abby even though he doesn't want to.
The movie worked for me on an emotional level. I thought it was very funny, too. I laughed out loud a lot, and the crowd (an almost full theater on opening night) laughed a lot, too.
One more thing. This movie accesses a trope that has bubbled to the surface of the zeitgeist a lot in the last 5-10 years: the Man-Child. Mike is an "aspiring" comedian when the movie starts, working nights behind the bar at a comedy club and not really trying to be a comedian. Very Man-Childish. He's often portrayed as a child: either as a complete newcomer to the comedy scene, when other grizzled comedians pass advice along to him; or, as the son of his parents, who don't treat him like an adult (by forcing him to take money, telling him to get his shit together, etc). Normally I have a lot of issues with the Man-Child, because the trope seems to have sprung from a collective dude hive mind. Man-children are often entitled and have a strange, unexplained appeal to the other characters around them, including their partners, who love them even as they spend their time smoking weed and playing video games. I think where Sleepwalk With Me moves past the trope is in the depth of Matt's character, who responds to his failed dreams with appropriate shame and a general existential angst. It seems like he loves Abby, and it's believable that she might love him, too. And I don't think he smokes weed or plays video games, which helps.
Sleepwalk With Me is the second movie I've seen in the last month or so that expands the Man-Child trope to make it more interesting (the other was Celeste and Jesse Forever).
Those two movies have a lot in common. They both explore characters who begin their films in stunted, childish relationships, who spend their screen time growing up and discovering their emotions.