This new sensor in the 5N receives great review. I'm really considering this 5N as a small back up beside my SLR. still my 2 concerns:
1. AF performance: the following is from dpreview.com
The NEX-5N relies on contrast detection to determine focus. In general this method is not as fast as the phase-detection systems found in DSLR cameras but in recent years the gap has closed dramatically. Unlike phase detection, contrast detection focussing systems must 'hunt' back and forth to establish maximum contrast, which denotes accurate focus. In low-contrast, low light scenes, this hunting takes longer, and as such, shooting with the 5N in this sort of environment can be time consuming and in some cases AF is simply not possible.
2. the lack of high quality E mount lenses to go with this great sensor: the 16mm f2.8 prime is not that great from what I've read, and $1000 carl Zeiss 24 mm prime is kind of bulky. I wish they have a quality pancake prime like the panasonic 17mm prime. I guess you can use A to E mount adapter to use A mount lenses but it would make a portable camera not compact anymore. But for people just shooting with kit lens and not considering lens upgrade, this camera is definitely a steal at $700 with APS-C sensor quality and easily outperforms the smaller micro4/3 format which costs as much.