Holding both my 6S and 7 in hand, here are my two cents.
- Liking the new colour of the matte black vs. the space grey
- New home button doesn't press down because it uses haptic feedback; it will definitely take time getting used to
- New "dual speakers" are excellent and is almost as good as the front facing ones in the Nexus 6P; it's a significant upgrade from the 6S
- The new screens have a much lower maximum brightness and a slightly higher maximum brightness when I compare them at 0% and 100% brightness
- They talked about wide gamut during the keynote, and all I know is that the colours on my 7 are a tad warmer than the 6S (I prefer the cooler 6S)
- Existing 6/6S screen protectors will fit granted the headset speaker is wide enough as it has gotten bigger to accommodate the new front design
- There isn't much of a difference in good lighting camera-wise, but the low light performance is better than the 6S for sure; 4.7" models now get OIS as well
- Better selfie camera that is much sharper with less grain
Pros
- Better front/back camera with wide colour gamut and optical image stabilization
- Brighter screen with wide colour gamut
- New "dual speakers" are amazing for media consumption
- IP67 dust/water resistance is nice; iFixit submerged their iPhone in an aquarium for several hours without any issues
- Slightly bigger battery that is said to give an extra 1-2 hours depending on usage
Cons
- Removal of headphone jack means having to carry an extra adapter or keeping it permanently on your headphones; it doesn't come in black
- Home button's haptic feedback.. you're either gonna love it or hate it
- Design is very similar to the 6S, although the new black colours are awesome
Costed me about $250 to go from my 6S 64GB to a 7 32GB, so I'm a happy camper. Downgrading in size doesn't bother me because I don't use much space, but 16GB was way too little.
A lot of people criticized Apple, but I think the 7 was a nice update to the 6S. Bigger battery, better cameras, better screen, IP67, and new speaker design. Some cons of course, but I can live with them.