The DCS-2330L has impressive night vision: specs say 15ft, but I can clearly see almost 3 times that distance at night.
The trick appears to be to ensure the IR doesn't hit a wall or something too close to the camera.
I had my camera initially mounted flush against a wall, and when the IR hit the wall inches away from the camera, night-vision dropped to around 5ft.
Re-positioning the camera makes a much greater night vision distance possible.