I have made and stickied this because otherwise closer towards launch when these forums pick up even more there will be a fair few confused people asking about these:
The wireless controllers run on 2xAA batteries. You can buy the single battery packs, OR the play and charge kit, which comes with the battery pack. This means you can charge the batterys when the console is off or on, while it's playing if you wish, and once charged use them wirelessly.
Correct me on this but does the battery pack come with a standalone charger of any form?