seems pretty good to me. i just played angry birds for about 2 hours with the screen on sort of bright (if i had to guess around %60-%70 brightness up)..it was full when i started playing, it's like this now...
my old 2nd gen would have been past half so it's good if your upgrading from 2nd gen
"Furthermore, the battery has a much lower capacity (3.44 watt-hours versus 5 on the iPhone 4). Yet, this device needs less energy as it doesnt have 3G connectivity."