I much prefer the size of the iPad mini over the iPad. That said, I wish the iPad mini had a better resolution. Then again, we have an iPad 2 at home and my wife uses it all the time.
As for Nexus 7 vs. iPad mini, I'd say Apple wins in terms of OS slickness, stability and consistency, and hardware quality. I just prefer the smaller size of the Nexus 7 with higher rez, and the ability to properly play MKV files, including off USB drives.
OS X & iOS: 27" iMac Core i7 870 | 13" MacBook Pro C2D 2.26 P8400 + SSD | 13" MacBook C2D 2.4 T8300 + SSD | iPad 2
Windows: X3400 Athlon II X3 435 | 11.6" 1810TZ Pentium SU4100 + SSD | Revo R3610 Atom 330 + SSD
Android: RAZR HD | Nexus 7