Apple's new iPad is a remarkable achievement in many ways. One of the most impressive aspects of the device is how much faster it is and how much better the display looks, yet it still keeps a good 9-10 hours of battery life like its predecessor. However, their is one interesting caveat that the folks at Ars Technica figured out, and it's a pretty important thing for owners to know. Apparently, they went to the trouble of testing the battery charge after it registered that it was at 100% capacity, and surprisingly found that the battery was not actually fully charged at that point. In fact, it required another full hour to completely charge the battery to maximum capacity. Here's a quote, This isn't necessarily a design flaw per se, but is really more of a limitation in accurate battery charge sensor technology. One other piece of useful advice comes from Apple themselves. They shared that it is a good idea to fully charge your iPad's battery to maximum at least once a month. Along with this new information, now we can be assured to improve the health and longevity of our new iPad's battery. Source: PhoneArena
I actually noticed this the first couple of days of usage. I almost returned it because I thought the battery was bad. One night I put it on the charger earlier than normal and it lasted much longer the next day.
I noticed the same thing with charging. It seemed like it was draining really fast until I charged it overnight.