I received my iPhone 4S the day it was released. It's become a policy for me to buy a new unlocked iPhone and a new iPad whenever Apple releases it. Even if I don't really need it, even if I pay the full price (I hate network operators).
I've used all the new features, and had fun on the first day asking funny questions to Siri. These tricks work mostly in english, and in french, I just find that too many things don't work, such as maps, wolfram alpha, thus reducing the scope of the assistant's usefulness.
Now I use it everyday, even if my calendar is not so full that I need to move appointments around, mostly for Reminders, Weather and alarms. It is handy. Actually, it makes using reminders a no-brainer: I've beenusing iOS 5 since mid-august, and never used Reminders. Since I have my new iPhone, I use it everyday, several times a day.
One of the things I noticed is that the combination of iPhone 4S and iOS 5 seem to give a much better accuracy for location. That's mostly helpful for me in 321Run, as it provides more info for users, and I'm happy when users don't complain about Gps in my app.
Even just with iOS 5 and an iPhone 4, the accuracy and behavior problems that have plagued the use of Gps for some people, such as my wife, seem to have disappeared. She would lose he signal, or get a location that was supposed to be accurate when in fact it was a gsm tower: her tracks would suddenly jump 3 km. It seems the transition is over, and I'm quite happy it is, and they stop playing with it.
Network wise, I didn't notice any improvement. But we have a much better network than At&T, or so it seems (I remember the low quality while in the US last summer).
The camera and video are surprisingly good, but still not good enough for low light situations when it comes to the camera. I'm quite happy I took the 32 Gb, but I think that 64 would be nice if you really take a lot of videos. For example I wonder what I will do on my next vacations. Maybe unload all videos and music first?
I don't know yet if iMessage is "disruptive" but it's nice, helpful and fast. I'll take an iPhone with a data card from 3 with me his weekend in London. I think it will be nice to have iMessage. What's fun and annoying at the same time is when all the devices I use start yelling at me atthe same time because I received a message. I need to clean up some of them in the settings.
I'll finish with the form factor. I think the iPhone 4 is a great shape, and very nice design, and I'm very happy they kept mostly the same design for the 4S. I wouldn't mind if they kept the same design for several iterations of the product, and I think they will. I hope they will, even: faster ramp up for the production, less difficulties with accessories (iPhone 1 dock is my reference for that), etc etc.