It takes me between 14-17 hours, but depends on my usage considering Wi-Fi is on for most of the time and either listen to MP3s or play heavy games (Asphalt 6, NFS Hot Pursuit) for at least an hour. Disappointingly, it's almost the same results when I was using rooted stock (13-15 hours). I guess I should consider updating less frequently, as my apps with online access is set to automatically update every hour (trying to exploit my employer's free Wi-Fi
With (very) light use though, it can last for full 48 hours.
Oh by the way, I'm also using the 2000mAH extended battery.