iPad accessories are supposed to make a great product even better. These aren't just attachments and add-ons, though; far from it, these accessories (and, at times, apps) enable the iPad to become anything you want. Do you want to turn your iPad into a larger-screened iPhone? There's an adaptor and application for that. Ditto when it comes to acquiring a digital camera and wishing that you had a portable photo studio with you.
What Each of the Different iPad Accessories Bring to the Table