This is a great little monitor with great picture quality & unbelievable battery life.
The monitor unit itself is akin to the size of a large mobile phone and surprisingly light, so can be carried around ina pocket or whatever quite easily. The battery life, when fully charged and not connected to the mains, will honestly last for hours and hours... i forget how long, as i didn't time it, but I tested it when first bought and made sure my first charge went from full to empty and I could not believe how long it lasted with both sound and picture - I'm fairly certain it was over 10 hours.
The picture is as good as you would want, or you could reasonably expect in a 2 inch or so screen - any better resolution would be a waste. Really nice how the unit converts to a black and white (also clear) infra-red image in low/no light conditions - i really didn't feel they made enough of this in the literature as I deliberately didn't want one of those units with leds that try to light up the dark room sufficiently to get a good picture. So this one has a great picture provided from a pitch black room, should you want it that way.
Sound is fine, nothing to report there.
The only extra feature that i thought could have improved it would have been display of the temperature in the camera room - but not a great worry as this 'does what it says on the tin' better than you would expect. They should blow their trumpet a little harder!
So in summary, I could not recommend this little piece of kit enough.
***** UPDATE Feb 2013 - bought a second unit for a second child - we wanted a backup in case the old one failed / plus we still use the old one to keep an eye on our first, now a toddler. The new one isn't as good as the one I reviewed above. The battery doesn't last as long, the reception isn't as strong and already (only three months in) one of the buttons has gone - the video on/off button on the top, so the image is either on or off all the time when plugged in. It's still ok as a monitor - but probably just average rather than great, and threrefore on the basis of this second unit I've bought, probably questionable value (at the discounted price of £110 currently - I think I paid less than £100 for each of the two units I've bought, but forget how much exactly). Aside from the dodgy button, the new one won't last through the night on battery alone and if i stray too far we momentarily lose reception. I guess they've made some 'efficiency savings' in the production process. A shame as my old one originally reviewed (now three years old) is still going strong and exhibits none of these problems. ***