So that Sony 16mm f2.8 E-mount lens is not the greatest lens ever made, but it is one of the cheapest, and the ONLY auto focus E-mount lens at 16mm or wider. If you need auto focus wide angle lens wider than the kit lens, your options are pretty limited. It's been more than two years since the introduction of the NEX system, and yet, the number of good lenses from Sony is pathetically few, especially small primes. But, back to the 16mm pan cake.
The weakest part of the Sony 16mm f2.8 lens is its edges. Although I think it's acceptable between f8-f11 for most casual use, there are clearly lenses that can do better than this. For me, I won't hesitate to use it and I find that it is good value for the money.
New Building Rising -- NEX-5N & Sony 16mm f2.8 Pancake
The Red Rocket -- NEX-5N & Sony 16mm f2.8 Pancake
Feverish Construction -- NEX-5N & Sony 16mm f2.8 Pancake
The Hyatt Hotel -- NEX-5N & Sony 16mm f2.8 Pancake