Very satisfying single campaign that is both ample long and non-stop action from start to finish.
The single campaign is not super long but it is far longer than many reviews have said. There is 18 missions so your looking at 12-15 good fun hours.
While not quite as good as Uncharted 2 this MW1 is far more polished and satisfying that many top shooters like Resistance and others. Just a good story and tremendous action that is fun and always something new on each level.
The missions are varied enough so they never get stale. Some missions are defending territory against overwhelming odds. Other missions you are hunting down high targets. Some missions you are going building to building and others you are out in the country side. Very good mix up.
The Brit campaign is far better for some reason. You will be taking on Russian Thugs and Islamic terrorist so that is always fun to eliminate. Get your gun and have fun Mr. Soap.