This is really a reply to all, but it's relevant to rc88288's post too...
First, let me say, I totally understand everybody's frustration. You're right to expect the phone to "just work" as promised. And battery issues are especially infuriating. I went through it too, on the upgrade to 10.3 for my 6s. And yes, Apple told me to do all the same things that didn't help... resets, etc... In the end, they heard enough noise to create the battery recall program and that's what did the trick and saved the phone.
So by all means, do keep protesting and making yourself heard. Especially, make use of the feedback link on Apple.com, because you're less likely to reach the ears of someone who can change course for Apple here on the user-supported forum.
That said, I want to bring you up to speed with what's happened on my phone, in case it will help you. Today, after skipping the 10.3.2 update entirely, I allowed both my iPad and iPhone 6s to upgrade to 10.3.3. So far, I'm happy to say there have been zero battery drainage issues with either, though it's only been a few hours. If anything, I might be getting better battery life from both.
I mention that not to gloat but because I wonder if it has anything to do with getting a battery replacement earlier. A lot of people who are still having problems seem to NOT have gotten the replacement battery during the recall. I wonder if Apple will need to widen that recall pool. I strongly suspect that's the case, that you who are having problems also have some kind of battery defect that's triggered by the firmware update.
Do consider it as a possibility and prod Apple to answer you on that question. They won't do so readily, when you first bring it up. So you have to keep pushing and prodding. Hope that helps someone.
P.S. I've been an Apple user, either directly or through my family when younger, since 1980 or so. Right from the start. The years I had to use an IBM Thinkpad for work... sucked. But then Jobs came back to Apple and I got back into the "family" again. I can't begin to count for you the number of MacBooks, iPods, iPads, and other Apple products I've had since. These days, I'm also a pretty happy shareholder.
All that said, I've been annoyed with one glitch or another many times across the products. An OS problem, a faulty lid, battery issues. But for the problems I've had, I've seen my friends on Samsung, HP, IBM, Motorola, etc go through much, much worse. I would never switch away from Apple for those poorer alternatives.
Particularly, to those that are using this issue as a reason to switch to Samsung, remember that they have had there own widely reported battery problems with several models in the last few years, including at least one that causes fires and keeps the Samsungs officially off airplanes. I'm just saying, don't be so quick to jump ship. You may land in a pool of piranha.