Wall wart adequacy

[Perl6_user]

I've been using the newly-arrived PBP, usually plugged in. In some sessions, the charge indicator drops below 100%, but still says it's charging. If that's true, it suggests that the wall-wart is unable to charge the machine at the rate it uses power. (Modest use, nothing dramatic.)

Is this a software problem, a failing unit, or is it an indication that a more puissant charger might be a good idea?