No premise. No plot. No villain. No point.

Rating: 4/10 (1 January 2012)

More critique than review.
First, Ethan being rogue was the premise of the first movie. We've been there, done that. Of course it was 15 years ago, so I imagine the writers hoped that most of the target audience are too young to remember that they've paid to see this before.
Second, out on their own is how the M:I stories should be, so there's no point to this ghost protocol guff. The writers have no idea what "disavowed" means. The IMF is a secret organization, so there's no reason to shut the whole organization down unless that secrecy has been compromised. It hasn't. They would instead disavow any knowledge of Hunt as a US operative, release some cover story to the Russians that he's a nut or terrorist, offer help in finding him and try to find him themselves. Which brings it back to the first movie's story.
And that bring us to the ridiculous US-and-Russia-could-enter-nuclear-war story. The Cold War is over. Two superpowers, who are even permanent members on the UN Security Council together, aren't going to war because an unidentified person who has no known political affiliations and no known agenda and who MAY be a US citizen was found to have set off a bomb. It's like it should be set in 1981.
This story has such weak justification and gaping plot holes. That the Russians wouldn't change their nuclear weapon activation codes because it will take them weeks to discover they are missing the activation device doesn't make sense. Just to be on the safe side after a bombing like that they'd change the codes regardless of whether they knew the device was missing or not. It makes no sense not to change the codes just in case the device isn't missing. As for plot holes there is no explanation as to how Hendricks knows Hunt's team is in the IMF at the same time as he is, so his broadcasting fake messages makes no sense. And likewise there is no explanation how the attack on the secretary's car comes about. Hunt doesn't even question how the car was found so quickly! It like the writers had the idea of putting a traitor in the IMF (it would have had to have been Brandt), but then realized that that would have made the similarities to the first movie way too obvious, and so abandoned the idea but forgot to remove those elements from the plot.
Third, the premise is abandoned as soon as it's begun. The hook for this film is that Hunt's team are cut off from IMF resources. I'm hoping to see them doing some tricky stuff on the fly; using their skills rather than gadgets to win. So it's a big let down that they are immediately given access to a freight train car full of goodies. Sure, they only take what they can carry, but what they can carry seems to be exactly what is needed. Hunt's climb up the Burj Khalifa would have been better if it had somehow been accomplished without the gloves. His abseiling with improvised rope down the Burj Khalifa is the kind of scene this movie should have had more of.
And bizarrely the equipment is constantly breaking down, putting them in the gadget-less situation that they should have been in to begin with. One glove stops working and Hunt has to climb with only the other. The mask-making machine inexplicably breaks moments before finishing its mask. Maybe the writers wanted the tension of the team without gadgets, but had no idea how to write it into the script, so things stop working at the last moment. Some of it's obviously for the comedy (the phone booth, meeting the broken glove re-stuck to the window), but that just highlights that the writers are padding out the action.
The villain is most vanilla I've seen in a big budget movie since Star Trek (2009). He's a cliché that exists only to constantly escape so that the story can be moved to the next action beat. Die Hard was a great action movie not only because the action was good, but Hans Gruber was a great villain.
Last, for every well filmed action sequence there is a very weak one. The foot and car chase in the sandstorm really didn't look like it was filmed in Dubai. It didn't even look like it was filmed outside. The sandstorm had the feeling of a cost cutting measure so that location shots weren't required. And half of the finale was set in the electrical room of a TV station with a very mediocre fist fight. That it was juxtaposed with the other fight happening in that amazing looking car park just highlighted how cheap it looked. And when will scriptwriters learn that nuclear devices are not exploded at ground level where half of the blast would be wasted into the ground?
M:I-GP is a film that really should have had much more development given to the plotting and script. I was disinterested in the characters and the premise. That is couldn't even manage one twist except for the last minute revelation about Hunt's wife that added nothing to the previous 132 minutes of mediocrity showed to me that the writers not only have no idea how to write action, but no idea how to write the M:I story that they want to tell.
Verdict: Eventually you should rent it if you want to be up to date for M:I5.