First things first, I found the first two Scary Movies appalling, and I borrowed this dvd on a friends suggestion.
I am happy to say I was pleasantly surprised! It seems the departure of the Wayans brothers from this franchise has revitalised it.
This film takes off movies such as Signs, 8mile, the Matrix, The Ring, The Others and more in the way Naked Gun and Airplane spoofed their respective movies. This is because one of the Zucker brothers directed this, and whilst its knowwhere near as good as his previous films, it's a huge improvement on Scary Movie 1 & 2. (How did they get away with the Michael Jackson spoof? Close to the knuckle and very funny!)
The extras are excellent, in particular the alternative ending, which is very interesting to watch (though thank God they went with the final cut, as the alternative simply isn't funny - but its completely different - spoofing the Hulk and quite lengthy).
A fun film, with adequate performances and very good extras.