Saw it. Damn! Had high hopes and was pretty let down. I thought it started OK (though thoroughly predictable), and then the time travel thing (which I was unfortunately spoiled about thanks to the local newspaper's headline - MIB Travels Back in Time to Entertain in the Present - GRRRRRR) was just lame. Why would K be so bummed about Will Smith's father dying? It wasn't his fault. And how would what have happened changed anything about K at all? It made no sense.
And the bad guy was too tough. He can kill all those guards but can't kill K? Just show up at his house and blast him....or shoot at him from the roof. Or send the evil creature thing.
Josh Brolin was good. Will Smith had his moments. But I would rank this movie below Battleship, which is a real surprise for me.
My score: C+. It's not worth seeing