well, i understand why you feel disappointed. we all get used to this feature. I mean we have adapted to this feature. It is too common for all products with rechargable battery.
On the other hand, if we have to discuss whether it is essential. Then it depends on what's your need.
I guess when we have 3 to 4 hours to get bs3 plug to AC power, then we can assume it is fully recharged. If your time is less than 3 hours, no matter there is indicator or not, it is not fully recharged. If there is around 4 hours, we are sure it is fully recharged, no matter there is indicator or not. In this view point, we cannot see any benefits of the full-charged state indicator.