This camera is very responsive, and takes great pictures. I use both a D300 and D700, but when I can't, or don't want to, carry the weight of a DSLR, this camera comes in very handy. It fits nicely in a larger coat pocket, even with the 30-110 attached. The LCD screen is nice, as is the build quality. The built in flash does a decent job.
Using the camera is a pleasure. The time to acquire focus is very good in decent light - it matches the quickness of a DSLR. It also has excellent focus tracking in good light. Unlike a Point and Shoot, pressing the shutter button results in the camera taking a picture (imagine that), instead of a pause while the camera attempts to work out focus, exposure, etc. The image quality is surprisingly good even with the smaller sensor. Focus speed and accuracy decrease as the light decreases, but, while I am used to the focus ability of Nikon DSLRs, the J1 still does a decent job when the light levels decrease. The frame rates available in continuous shooting modes is awesome.
Another thing that prompted my purchase was the camera's video ability. Neither of my DSLRs have the ability to record video, so I wanted something that offered good quality video. The camera's video capability is very good. I don't have a lot of video experience, but am very pleased with the J1's video focus and overall video quality.
A few minor gripes: You cannot turn off the image review. After a photo, or series of photos, the image is displayed on the LCD. A half press of the shutter will clear it, and allow you to continue shooting. Hopefully this will be something addressed in future firmware updates. The use of the Feature button could also be improved. It's use is determined by the shooting mode the camera is in, and what you can use it for is very limited. It would be great if this button could be customized, or used like the INFO button on Nikon's DSLRs, allowing quick access to different shooting settings.