What's the Draw of 3D?

History certainly seems to repeat itself. Films in 3D have been around for a while but seem to have peaks and valleys in their popularity. With the last burst of 3D cinema occurring close to thirty years ago (perhaps it follows the remake timeline), more films recently have been released relying on the concept of adding that extra dimension to movies. With James Cameron's much publicized Avatar set to drop later this month, 3D films could be facing a huge resurgence depending on this film's success.

But my question stems from an article quoting James Gianopulos, the CEO of Fox who was overseeing the production of Avatar:

"As Jim says, we experience the world in 3D, why should we experience film any different?"

Having only seen one film in theaters with 3D segments (for the record, that was the terrible Freddy's Dead), I can't really speak for how well depth perception is really conveyed. My questions are, if films have been shot in regular 2D for decades consistently, with 3D appearing as a fad with its many resurgences and declines, is 3D really that effective? Is it here to stay? Did it make Jaws III a better movie at the theater than what I saw at home?