I feel I should make my stance a little clearer on this.
Like many others here, I would have LOVED to see a 4000mAh battery in the Note. So when I heard that it was probably going to be 3500mAh, I was a bit let-down.
I think for a lot of us, 3500mAh just doesn't look as large as 4000mAh and even though it's only 2.8% smaller than an S7 edge, just the thought of having a Note that has a battery that's even ever-so-slightly smaller than an S-line device is hard to stomach. I think that's where a lot of the disappointment comes.
However, on the brighter side of things, it is at least a 500mAh bump from the Note5, which is pretty significant and it'll likely be more efficient, meaning that it might roughly be similar to the S7e in terms of overall battery life (not holding my breath, though). Which is sweet, but to those who want more, it might be disappointing because there's always that feeling of "wanting more", especially heavy users and those who are accustomed to the Note having a bigger battery than the S-line phone.
In short, it's still an improvement over the Note5 in terms of battery capacity and efficiency, and if it does boast some efficiency improvements over the S7, might even be roughly similar to the S7e, despite having a larger display (though I'm still not holding my breath, but it should still be pretty good). However, it's hard for some to NOT think about how much better it could be with a larger cell, but given that it is still a significant improvement over my LG G4 in both regards, and a MASSIVE improvement over my M7, it doesn't really bug me as much.
However, YMMV.
That said, Samsung. If you're listening, can we have a Note8 with a 8.7mm thick chassis, slightly larger display and being able to squeeze in a larger battery through some genius rearrangement of components even with an S Pen plus the usual efficiency improvements? Not that the Note7 isn't sufficient for my usage, but still, one needs progress, right?
(As a side note, the Note7 might be slightly thicker than the Note5. And yes, can we end this race for thinner phones, please? The S7 got quite a number of welcome improvements, especially having a bigger battery and a smaller camera hump from that 1mm increase in thickness. There's no need to go any thinner. 7.5mm is my limit.)