G12 is excellent. A Nex is better, but it's only as compact as the G12 if you stick with the 16mm prime. If you lust after a 24mm prime with real bokeh, then this is the one for you. If not, then the G series has much to offer. Note that the G12 isn't as fast as you'd think ,and although it's quicker than the P5000 it's still no processing demon.
[I bought the Nex as a stopgap/backup for a Leica, and as yet I'm still having too much fun with the little guy to look at M bodies.... at least for a few weeks! There's some serious debating between a new Summarit and a secondhand Summicron going on, though, over at this end... I overlooked the Nex for a long time as a result of my misconceptions about the camera, and Sony.