I would stay away from the NX system. Samsung talked a good game about being a serious player in the mirrorless space, but their actual conduct has turned the otherwise promising NX system into a joke.
Seems like a great system to me, with wonderful lenses.
GXR / Pen / G3 / NEX .... there are some great systems out there. Loyalty to a brand means nothing to that company bar $$$ so instead think which camera will suit you best. Having looked at all of these the NEX 5n is a wonderful buy for my uses but YMMV.
My dilemma is I am concerened about IQ, but it is not a complete deal breaker. I am also considering the Ricoh GXR with 28mm lens and bigger sensor.
Is the $200 more for the GXR worth it? I know the Q price may come down soon.
If you are considering the GXR with 28mm, consider the Ricoh GR DIGITAL IV. I know it is not interchangeable, but it is a sweet camera. And it runs significantly CHEAPER than the Q. Cake => Eat it too.
As for me, I've been a loyal Pentaxian since the 70's. I have two digital bodies and several film bodies. But I took the $769.99 pricetag for the Q and purchased two cameras... a very compact and extremely capable Lumix LX-5 (349.00) AND an Olympus EPM-1 Kit (399.00). I feel the IQ of either is better than the Q. In fact for the sensor size, the LX-5 is astounding. Frankly I would not want a camera smaller than the LX-5 let alone 30% smaller. If this makes me a bad person, so be it... heh.
Yeah, my two cameras (for the price of one Q) sure are pigs next to that Q! That ~ 1.15 cm x .6 cm is REALLY going to be a huge difference... especially when faced with the IQ of Micro 4/3rds.
Anyway. FWIW, good luck to the OP with your decision.