I got my 6S Plus yesterday, so far everything is perfect except for one pretty significant thing. The battery life is much better, everything is perfectly smooth and it multitasks like a dream.
The big problem is that it will randomly lose internet connection. It's happened four times now, for 5-15 minutes the phone will just completely lose the ability to connect to the internet. Wi-Fi or 4G. It happened when I was trying to activate the phone and has happened twice yesterday and once today. It says it's connected to Wi-Fi or 4G, but nothing will load on any app. This happened on both stock iOS and 9.0.2, and not in areas where there could be data interference. It's the only blemish on an otherwise great experience. Not sure if it's an iOS or hardware fault, as AFAIK the only bugs have been cellular related and this affects Wi-Fi too. If it happens over the weekend I'll probably exchange the phone as obviously I can't have the internet die on me at important times.