There are so many millions of iPad users that no simple explanation can cover all use cases. But my take, since last year, has been that the full-size iPad is best seen as an alternative to a laptop, and the iPad Mini as a supplement to a laptop.Daring Fireball: The iPad Air.
Yes! Yes! Since I got my iPad I no longer use a laptop. In fact I sold my laptop and use my iMac for "heavy lifting".