It seems the people who really enjoyed this flick as an example of noir are folks who focus a lot more on cinematography and film-making than the average viewer. (I don't know if the helicopter shots, for instance, were ground-breaking.) However, I can say that as simply a casual viewer who enjoys a good noir film, this one missed the mark. Is it noir or sappy romance? I felt like the director couldn't decide. The main actors seemed too baby-faced to carry off noir, imho, since the hardened characters in noir plots usually need to be a little bit more mature to have gained their worldly experiences. When compared with films like "Double Indemnity" and "Touch of Evil," "They Live by Night" just can't hold its own. Unless you're a total noir buff, I'd skip this one. There's even an old Nancy Davis (Reagan) film called "Shadow on the Wall" that few people have seen that I liked better than this one, fwiw.
Review of They Live by Night
