One of the things I am unhappy with the NEX-5 is that the auto focus system is much worse than the Panasonic G1 or GF-1. The G1's focus is nearly always fast and sure. The NEX on the other hand, has trouble focusing evening in very good light. Most of the pictures I shot had to be focus adjusted by hand before they were taken. So, it's auto focus system is nearly useless for low light work.
I am happy to find that ISO 1600 is usable on the NEX-5. It's comparable to the 5-year old 1D Mark IIn.
Skywheel at night -- NEX-5 & 16mm f2.8 Pancake. Click to see larger.
LED Water Fountain -- NEX-5 & 16mm f2.8 Pancake. Click to enlarge.
Dome of the Fallsview Casino's water fountain at entrance -- NEX-5 & 16mm f2.8 Pancake.