Just upgraded from my 6 to 6s.
Can't help but feel abit underwhelming.
Yes, the apps switches abit faster and the apps/games load abit faster but not really significant. The in-app and in-game experience are pretty much the same.
For the safari pages loading, compared with both phones side by side, again almost same experience, nothing to shout about.
For the 3d touch, those who have jailbroken our last gen iphone, can installed the software based version so in comparing that to the genuine tactile 3d touch, it's nothing really new. Feels really similar actually.
If we google around looking for 3d touch apps, there's only so few supported apps, yeah understood it is just 3-4 months since apple introduced 3d touch to the world so might takes time for the developer to adapt to it.
Overall, just feels the 6S is more of a future proof phone for now. Waiting for better things (read apps) to be fully optimised

Just my 2 cents