What magicj said. To date, almost no one has hit on functionality, style, size, and price.
No one offers a superior experience, and almost every one suffers from some fatal flaw on the software side of the fence. (No email RIM? Really?)
At best, their primary reason to buy seems to be: "Hey! We have a tablet too!" When that gets no response they then frantically play the Flash card, to which many people (including me) yawn and say, "Who cares?"
I get along just fine...