Well I have observed this feature conciously both in extreme traffic and relaxed one, and I can say that in number to number traffic it's useless and I have to switch it off, but where there is seamless traffic with occasional signals, tolls on highways, airport parking lane etc it's actually quite useful, it's great when fuel stops burning unnecessarily. So yes, not really a must have, but not that worse to be honest. Also regarding battery, I honestly don't think it's going to drain it especially if you switch it off like I do where I know I am going to face heavy traffic on my trip , I don't have to think about it, but has eventually became a habit and it doesn't really irritate me.