Yesterday it gave me about 5 hrs with initial factory charge and really heavy wifi/3g usage; had about 20% maybe before I plugged again? I also played Asphalt and Angry Birds for about 40 min
I am still still testing and learning the tablet's behavior so I don't want to give a serious review yet, but I am happy so far.
This is not a dedicated e-reader but a tablet, almost a really cool and small netbook so that should keep clear expectations about things like battery's life and screen's brightness.