This is just plain stupid. It makes extra batteries harder to find and more expensive. Sony, by contrast, has the common sense to use the same battery sizes for a few generations. The latter will have somewhat higher resolution. However, the raw number of pixels does not tell the entire story, since some of them are used for the image stabilizer margin rather than the main picture.
Sound quality is generally excellent.
However, there is no shielding for the microphones, so wind noise is very objectionable outdoors, even when the wind reduction option is chosen. One inevitable shortcoming of having a tiny camcorder is that the built-in microphones pick up some motor noise. On the plus side, the DV3 has a microphone input jack, so you can use a separate mike. It also has a headphone jack, so you can check the sound. The Sony TR3300, a top quality Hi-8 camcorder, is included for comparison.