Saw this last friday - had no idea what it was about outside of knowing Chris Rock was in it. I actually liked it quite a bit it was at times laugh out loud funny and other times a pretty serious look into the life of a troubled comedian. I don't believe Chris Rock has a lot of range acting, but he essentially played himself so it worked well. Definitely one of the most pleasant surprises in terms of movies I have seen this year. Kevin Hart (i know he is a polarizing celeb) really has a cameo role in the film and isn't a main character if that will help you decide whether or not to go see this film.
I saw it yesterday. Like YoYo I had no idea what to expect. It went from funny to serious, overall I liked it. Chris Rock more or less being himself.