Kew Beach -- NEX-5N & Canon FD 55mm f1.2. Click for larger.
There are few things that I really like about the NEX-5N over the original NEX-5. First thing first, image quality is markedly improved. Yes, there doesn't seem to be much difference when compared shots in perfect studio lighting, but anyone who have used both the NEX-5 and NEX-5N can tell you there is a big difference. This is especially true on high ISO.
First Curtain Shutter: This is one of the best new features that I really like. It reduces vibration on the camera and is quieter. I can consistently take sharper pictures at lower shutter speed than I could with the NEX-5.
Dust Shaker: on the NEX-5, this was good as nothing. Since I changed lenses a lot, I found the sensor to be ALWAYS dirty with dust particles. The new dust shaking is far more effective. I have seen any dust in my pictures yet.
Battery Life: this is slightly improved, but still light years behind Canon DSLRs. On my 1D III, I can get at least 2000 shots before the battery is depleted. Even on the T2i, battery lasts more than twice as long as the Sony NEX-5/N.
Overall, the new features are more than worth the upgrade price. I am very happy with the NEX-5N. I would be happier still when I can get an EVF for it.