I love my 6.
Love it.
However, I wish I'd got Silver (I have Space Grey) so I will upgrade for that reason alone.
The only reason I didn't exchange my 6 for Silver is because I have a (drum roll!) perfect unit.
No dead pixels, no light bleed, no cosmetic defects, no dust under the screen or camera cover, great battery life ... so I stuck with it.
I have had issues with every other iPhone, so this was a new & great experience for me.
Any improved specs on the 6S will be bonus (I'm hoping for this "DSLR quality camera" that we've heard about).
I'll also be in the market for a new iPad, as I'm irritation by the animation lag on my (also perfect, otherwise) 4th Gen ...