The point about the back button was just weird. It's a button, which is for going "back". In literally every app with multiple screens this is a fairly obvious concept, but on Android you have the benefit of not having to allocate screen real estate to it, and having the button conveniently thumb-reachable.
I have only used Android as my primary phone. But, I am still confounded by the back button. For example, I am using twitter and get a notification ( from say Facebook ) and jump in to the app from the notification drawer. I see the photo, like it and want to go back to the twitter app. I hit back expecting to go to Twitter but it takes me to the facebook feed. This is not "wrong" but seems messy.
I wish that Android makes it more clear to app makers what the back button should/can do, and then make them adopt a similar behaviour.
