I took my new Sony Nex-5n with the kit 18-55 lens out to shoot a family birthday party a couple of weeks ago. Here are my initial thoughts.
I was shooting indoors with moderately poor lighting. Focusing was relatively quick although it did get fooled a few times when there was strong backlighting from a row of windows along one wall. The automatic focus point selection wasn't bad but wasn't great either - I need to set this on using the center focus point and then recompose.
I shoot in raw - many photos at ISO 3200 were perfectly usable for my purposes (screen and small prints) with a little noise reduction in Lightroom. The kit zoom gets to f/5.6 pretty quickly so it wasn't optimal for indoor, ambient light shooting.
The flash was a disappointment - I tried the fill flash setting but everything I got was way blown out. I haven't had time to tweak this but maybe there is a setting I'm missing. Otherwise they're going to need a firmware update as the flash is close to unusable.
Auto white balance in the camera was ok, but most of the photos benefited from some WB adjustment in Lightroom.
The camera handles very well. Tilting the screen out to shoot from the hip is a nice feature, as is the touch-to-focus.