There are some software problems with the charging behavior. The OS2008 update released yesterday addresses one of them, though it's not entirely clear if it solves everything.

One thing I've noticed is that if I use the unit on the charger and then turn it off, it says "Charging", but it really isn't. No matter how long I leave it, charging does not complete and the battery charge does not increase. If I unplug it for a minute, then plug the charger in again, the charge normally completes quickly.