For this sequel, the filmmakers decided to go with the idea that more is better. There are cameras than just the one from the last movie and there are more characters than just one couple. But more does not make better. In fact, it decreases the suspense. More means there is less 'alone' time for the characters. Also, the fear is spread amongst more people; therefore, it is felt less by each.
The film Paranormal Activity scared the crap out of me. There were long, static shots of a room and an occasional event. This time, the long shots are much shorter and since there are multiple cameras, no room is the main focus like the bedroom was last time. Furthermore, there was no build up to an event last time. A door would slam or the sheet would rustle all without warning. Now there is a low, rumbling bass noise which signals a coming event. This takes most of the fear of anticipation out of the scene.
The plot is actually connected to the previous film but I won't give away how. The idea of a sequel to Paranormal Activity is fine and the script works...but there is too much activity going on to make it truly paranormal. If you haven't seen the first one, I highly recommend it. Skip this one.