Nexus 7 is my fourth Android device, second Nexus (current phone is Galaxy Nexus), but first tablet.
I had no interest in tablets because you basically had two options: Cheaper tablets with specs that my phone would put to shame, and more expensive tablets that, IMO, were not as useful as similarly priced laptops. Additionally, Android tablets seemed to be having some growing pains, and I'm not touching an iPad (I don't like Apple's business practices and refuse to purchase anything they make.)
The Nexus 7 gives high end specs, in a size that I like, for a price far below the "might as well buy a laptop" threshold. The fact that it's also a Google Nexus branded device certainly helped push me toward buying it.