Many people have reported that the Battery Watcher app doesn't update very often on their Droids (or Droid Xs). Unfortunately, that's just the information that the phone provides. It only gives 10% increments until it gets below about 20% and then it gives 5%. Worse, the phone reports that it can give 1% increments, which is why the details screen shows Accuracy 1%.
I plan to implement a workaround for the latter issue soon so that it reports the correct values on Droids. I'm not sure there's much I can do about the 10% increments themselves though; it seems to be a limitation of the phone itself.