It comes with wall charger and 2x batteries. So I swap them once a week or so.
Anyway, lets cut to the chase;
They have always performed as good as my stock battery. Actually I tried my stock battery last week and it gave me the same battery life. 38 hours vs 42 hours to be exact. (wifi on all the time, 15 minutes of calls, 30 minutes of gps navigation, 30 minutes of web browsing, 4 widgets, 15-30 minutes of facebook, twitter, football results etc.. apps)
So, if you want cheap batteries that (almost) does what it says on the tin, yiboyuan is the way to go.
( I'm not Chinese by any means )