Wow. For the first time this summer I've left a movie not feeling like I'd been forcibly penetrated.
MIB 3 was a very fun romp, with an tear-at-your-heartstrings ending that was just about perfect. This is the type of movie that CGI was made for. It's unobtrusively there to help tell the story, but not be the story. (Are you listening, George Lucas?)
Casting Josh Brolin as a young Tommy Lee Jones was sheer genius.
All I can say is go see it—especially if you liked its two predecessors.
The first one was great in it's own, as it established who the main characters are and what their job is.
The second one flat out sucked.
The third was was by far, the absolute best of the trilogy. They story, the makeup, and the supurb acting on Josh Brolin as a younger Agent K.