Very competent third MIB film, which is always a surprise, given that money is the main factor in making a 'threequel'. Josh Brolin is fine as a very young K (same character played by the very old and shockingly craggy Tommy Lee Jones - high definition isn't his best friend), Will Smith is great and gets the best lines, while The Flight of the Conchords Jemaine Clement provides a very satisfying baddy as Boris the Animal.
The plot of J having to time travel back to save the world and his partner wasn't out of place in a sci-fi film either.
I left very happy that the special effects, monsters and general feel of the film was right on target for bonhomie. I daresay MIB 4 is being quietly thought of right now. Go if you want a diverting 90 minutes of very simple fun.