Not worrying about battery life on an iPhone again is life changing (in the most first-world problem sort of way). With my 5S, I was constantly worrying about it, always trying to time the last charge cycle with the night's activities.
I'd planned on abusing the no-restocking fee return period to try it, dead set on returning the 6 Plus as soon as I found a 6 in stock. But after only a couple of days, the battery life alone has sold me. The other benefits are just icing on the cake. Sure, there are a couple of downsides, I'll get into those soon enough when I write an actual impression/review of this. For now, I think the upside has far outweighed the bad.