The battery lists a capacity of 3.44 Watt-hours.
Like all other revisions of the iPod Touch, the battery is soldered to the logic board. This isn't a surprise given the slim form factor of the iPod, but we wish Apple would make battery replacement easier.
Fortunately, compared to the 3rd Generation Touch, Apple did add more space between the battery's three solder points (on the orange ribbon just to the left of the battery). This should make the soldering job a little easier when replacing the battery, as there's less chance of accidentally bridging the contacts.