I was one with an S6 who did rush over to the Apple Store app on my iPad
2 weeks after it became available. FYI, I got 235$ for my S6 on trade in. The S7 larger screen is a big difference for me and my far sightedness. The buttons are bigger too so entering the passcode, which we’ll all do a lot, I’d now done with more precision. The keyboard is actually usable now IF I swipe. S6 it just was too small for the keyboard app I used. The surprise plus feature was the fast charging. I was in a good charging rhythm on S6 (coffee, shower breakfast while it charged). But i did need to take it not fully charged sometimes. The fast charge has eliminated that and allowed in those odd circumstances to get a quick jolt of juice when needed.
It has a bit of a different look, curved is a bit noticeable, but not huge. Your band choice is much much more of a aesthetic. The added toughness to the Watch glass is fortunately something I can’t tell you if it has made a difference. That’s the specs on it.
If none of this seems applicable to you, I’d recommend keep S6 and wait to see what S8 brings. S6 was my first AW and I loved it. But I can say many tech channels said ‘meh’ to S7 so I was concerned I’d wasted a buy. Imho it is much more of an upgrade than it was given credit for.