My girl bought a J1 and I must admit I really like it. The auto focus is very snappy and spot on. The auto focus on a friend's NEX5 was so sluggish compared to her J1. The NEX missed focus and hunted around a lot while the J1 was spot on every time with the same subject! The only time the J1 missed focus was during macro close-up shots. It never had trouble snapping into focus up close, it just sometimes focused on the wrong spot.
The electronic shutter is lighting fast. There is no shutter lag. The J1 is so quite that I often mistakenly shot 3 or 5 photos thinking I'd only taken one. You can mute the shutter and AF lock sounds and have a completely silent camera which is really great. The NEX shutter sounds too much like a chipmunk sneezing. After shooting with the J1 I had a hard time going back to my loud and bulky DSLR.
Even my similarly sized Sony Cyber-shot point & shoot handles like crap now after using the J1. The J1 menu is very clean and easy to use. I don't really like the cheapish feel of the smooth plastic body design but it's not as bad as I thought it would be to hold.
Video is good but the built-in microphone picks up a lot of camera body noise like the neck strap moving around or your fingers changing grip. I didn't like the placement of the video recording button. I kept confusing it with the shutter but I got use to it after a while.
The pop-up flash feels a bit cheap and it sticks so far out that I'm afraid it's going to get caught up on something and break off. The flash design seems very vulnerable to me and is also pretty weak.
Image quality is very good. It's not DSLR good but it's much better than a point & shoot. I didn't pixel peep the shots too much but I liked what I saw. The use of a smaller sensor wasn't an issue against the NEX. A few high ISO shots did seem a bit too much like watercolors but not as bad as some Sony cameras I've tried.