Okay, lets get this over with first - I am 45 years old. I'm not the audience for this film. I accept that. My 11 year old son and his friend (also 11) enjoyed the film and that's what matters. I liked Monsters Inc. I thought it was an interesting twist on being scared as a child. Monsters Uni is a prequel to the first film. For me, I didn't think it was as good as the first film in the series. There were some moments that were good but just not enough of them. This isn't to say it's a terrible film, it is an okay film but don't expect to see anything you haven't already seen from Monsters Inc. Also expect a lot of moments that try and illustrate why working as part of a team is a better thing than being selfish and doing it all yourself. I felt the film laboured this message, to the detriment of humour.
It's the story of two monsters who attend the Scare school at Monsters University, one who is naturally scary but doesn't work hard and another who is not scary but does work hard. They start out as rivals and through the course of events earn each others respect.