The close up of the car pulling up, creates an eerie atmosphere. The camera placement was effective and gave a viewpoint from inside the hole.
Editing
The flashbacks provide a back story, also the white flicker between flashbacks changes between the current proceedings and the past.
Mise-en-scene
The close-ups gave a brief idea of the goings on but didn't reveal too much information, which built suspense.
Soundtrack
The opening soundtrack also contributes to the atmosphere and build up to the film.The continuous flow of the soundtrack maintains the mood throughout.
Titles
The titles were simply and easy to read without distracting the viewer from the video.
ISpy largely consists of panning long shots and short close-ups. A little shaky in some of the earlier scenes but it adds to the atmosphere while the supposed stalker crouches in the bushes, looking into the house. It often uses the light to emphasize it's effect, such as while the stalker is walking along the street, but even though it focuses the viewers attention it is also too dark for the viewer to be able to see the scene clearly. Even though it is largely a single individual walking throughout the clips, with the music this builds onto the atmosphere.
ISpy suffers from the fact that it's scenes have not been filmed at a similar time, and during the beginning, it flips from daylight scenes to night scenes without any pause. The fading to white during the clip transitions seperates the clips quite effectively even though they don't really have much continuity.
The soundtrack is builds the atmosphere and gives it it's mysterious quality, improving the feeling of suspense.
The titles are integrated throughout the sequence, and play throughout the opening. They are fairly subtle and don't draw much seperate attention to themselves.