Changing settings can be tortuous depending on what you're looking to adjust. The Menu button gets you into a majority of your options, but important settings are buried three levels deep, and there doesn't appear to be any order. For example, switching between MPEG-2 and AVCHD--one of the major reasons for buying this model--requires you to press the Menu button go to Basic Settings, find the selection titled Stream Format and then choose either SD Video, which is, in fact, MPEG-2, or AVCHD. Then once you're back out, you have to hit Menu again, find Video Quality and select what recording speed you want to use. True, this probably isn't a setting you'll be changing all that often, but it's illustrative of the rest of the menu system, so if you're easily intimidated by digging through settings, you may want to try the JVC before buying.
Recording speed options for AVCHD (.MTS files) include XP at 17Mbps, a 12Mbps SP mode, or EP video at 5Mbps. JVC's MPEG-2 TS--recorded as .TOD files--are 26.6 Mbps variable bit rate (VBR) when set to full high definition (FHD) or 27Mbps in 1,440 CBR (constant bit rate). The 120GB hard drive will store up to 10 hours of FHD MPEG-2 video or 15 hours of the more compressed AVCHD format at XP quality.
Video quality on the whole is very good. Colors lean more toward saturated than natural, but are definitely pleasing and enhance the high-resolution video. This was particularly true when recording in MPEG-2 TS, which produced a more consistent tonal range as compared to the more digital-artifact blockiness of AVCHD recordings. White balance, when left in Auto, was a bit warm and dull; it's definitely best to use the manual white balance option or one of the three presets (Fine, Cloud, or Halogen).
Low-light performance was better than expected and actually quite good. There was some noticeable off-color noise, but the amount was certainly acceptable for dim shooting conditions. Also, typical of most consumer camcorder auto-focus systems, the HD40 tended to hunt in low-light shooting, causing it to bounce in and out of focus. Not surprisingly, the higher-bit-rate MPEG-2 TS presented finer detail and smoother-looking video than the AVCHD results. But frankly, as long as you're shooting in good lighting and unless you're really examining the video you'd be hard pressed to see a significant difference.
Photo quality is OK for a camcorder. It won't replace a dedicated point-and-shoot camera, but it's there if you need it.
For a high-definition camcorder priced less than $1,000, the JVC Everio GZ-HD40 has a lot to offer--especially if you're into manual settings and are not easily intimidated by digging through a convoluted menu system. However, the lack of optical image stabilization is regrettable for a camcorder of this caliber.