It depends on what you're doing of course. Normal usage (playing music/Youtube, browsing firefox, coding, opening up some PDFs) gives me about 6-8 hours I'd say, I get about 3 hours of (modded) minecraft, which is quite the battery drain. this is on Gentoo (Awesome as WM) so the background drain is pretty low. It's good enough that I never really pay attention to it.

upower says the battery is designed to store up to 48Wh, with a maximum design capacity of 53Wh.