Apparently gingerbread stops charging when the battery gets to 100% . I guess this puts less wear on the battery. But it is kind of frustrating to wake up with a battery of only 70 or 80% given the that the battery life on these devices isn't great. On mine I never get 24 hours anymore, but that's probably due to daemons.
Maybe a charging schedule could be implemented in some way, like "next Alarm minus average charging time" ?
It should wake up with anything between 95 and 100%. Anything less and either you're charger/battery/phone is doing something wrong.
Turning off the device and letting it sit in the charger (reconnect the charger) should fill the charge to 100% from whatever it it in a couple of minutes (10-30) while you wake up and get you're stuff.