I've got a 10" iPad and a 64gb Playbook. Purely from a physical size point of view the iPad is too big and the Playbook is too small!
The PB is a much handier size, fits in pocket, courier bag etc, but i do find the keyboard just a bit small for my fat fingers. I suspect all 7" pads are the same. In terms of performance, I can't fault it - superb screen, fast, and well built. It has no 3G but if necessary I use my phone as a 3G hotspot. Works well. The camera** is excellent and the video camera superb. Mine is mainly used for browsing, some emialing, plus occasional mapping, letter writing, normal sort of stuff. Don't think there are too many apps for it, but to be honest, who cares, I haven't felt deprived as a consequence. I don't play games on it apart from Tetris.
At such a giveaway price, the PB is well worth considering, and gets my vote.
** Has the Nexus got a camera?