There are times that I keep wishing to have a nice zoom or a macro. So NEX 7 seems like a great camera for that, although SONY is lacking decent lenses in that format in my opinion. I'm also not sure just how comfortable I would be with investing money into E mount, but that's a whole other consideration.
I now have used the Nex5n (kit and 24/1.8) a bit more side by side with a M9 (with 35 and 50 Lux asph)
When it is just about IQ I clearly prefer the Leica, because:
a) color and tones look different, the Leica color I prefer, but l guess its a question of taste
b)noise: The M9 at ISO 1250 beats clearly the Nex at 1600 ISO IMO.
c) Focus....For shallow DOF I get better results with the M9 - I know where I focus (eye vs nose) and it works. The Nex AF is ok but as soon as shooting shallow DOF I find the AF points too big and sometimes get the eyes very slightly out of focus for example. Focus peaking is fine, but also doesnnt allways works totally accurate IMO. And magnifier I dont like because I dont see the whole subject any more.
However with the Kit outside and a little more DOF the AF is fine.
But then the Nex offers zoom, it is very fast, I like the swivel display, it does video, and even if I prefer IQ of the M9 the Nex IQ is still very good.
The combo of the Kit and the 24/1.8 allwos to use the camera both in good and low light.
So for me the Nex for felexibility, for casual and for low weight,...bike tours, skiing, family events, things like that.