I didn't want to rent this one and I deliberately avoided it in the theater, since I didn't like the first two. They were full of plot holes and stupid ideas that were constantly jolting me out of any kind of suspension of disbelief that I might have had going into them.
As before, Tom Cruise plays Ethan Hunt, the agent who goes out and takes on impossible missions (thus the title). In this movie, he's retired, and one of the students he has trained is in trouble and he rushes off to rescue her.
This is just a good, solid action movie. I liked it far more than I expected to.
It's worth your time, especially if you were avoiding it like I was. Lots of fun.