Plenty of threads relating to the lawsuit cover it all fairly well, but it wasn't about updates decreasing battery life.So what was the lawsuit about then? Battery fatigue, was it not? Anyway, this isn’t rare — people downloading the latest iOS update only to find their phones draining faster the next morning. Oh, and it’s always conveniently in time for the release of the newest iPhone.
As far as it not being rare that people notice more of a battery drain right after updating, that certainly happens, and in many of those cases it stabilizes after a few days. In some cases there is still more of an ongoing effect. At the same time there are plenty who don't really experience much in terms of noticeable battery effects one way or another, and there are even some that actually see some improvements at times. It can be different for different people, but usually there isn't necessarily some sort of a general noticeable effect that most feel to some point where they are really impacted by it.