Now in its second generation, the NEX line has proven to be popular; I generally liked the NEX-5 (we never reviewed the NEX-3), thanks to excellent photo quality and an attractive, compact design, though I still think the line is a bit expensive for people seeking to upgrade from a point-and-shoot.
The C3 incorporates an unnecessarily higher-resolution sensor than both the earlier models, bumping from about 14 megapixels to 16. It's not, however, the same 16-megapixel sensor that's in older models like the SLT-A55. At least the photo quality doesn't suffer from the resolution increase, and given the different sensors in the C3 and the NEX-5, the photos look surprisingly similar, even at high ISO sensitivities.
The camera's noise profile is quite good up through ISO 400. Photos still look clean at ISO 800, though you can start to see some mottling from the noise-reduction algorithms; by ISO 1600, detail degradation becomes visible and hot pixels start to appear. It does a solid job at ISO 3200--not clean, but still usable in many circumstances. (Since I'm still waiting for software raw support, I can only comment on the camera's built-in noise reduction.)