It's not marvellous, because of the small single chip sensor, but still useable. I took footage last week in a dark pub. Most of the time I used an on-camera light, but was also able to get some good candid shots with the light switched off. As long as there is some light near the subject you can still get reasonable footage, although of course there is some graininess. The shots with the on-camera light turned out very clean and colourful.
Apparently if you have time to set up the shot, you can minimise graininess using the exposure lock (auto mode supposedly increases gain to max before fully opening the iris - with exposure lock you can get the iris fully open before adding gain as necessary.)
I have to say though, that if you are expecting PD170/VX2100 type low light performance you will be disappointed. I don't think any of the small HDV cams come close to those old workhorses.