Ok, had it nearly a day so here are some brief thoughts:
Size & Ergonomics:
Coming from a Z3 Compact, size was always going to be an issue. I'd previously sent back an S6 as I couldn't get on with it's ergomics and software. It's pretty big, it's the same size as a Note1/2 I think which at the time people were screaming "it's too big" but this seems to be the norm now. The back is tapered on the sides, which makes holding it quite good. It fits quite nicely in the hand and doesn't feel uncomfortable. I much prefer it to the S6.
Screen:
It's big and it's bright, it's really high resolution so no pixels in sight. It's obviously not AMOLED, but you can tell it's been tweaked for vibrancy and saturation. It would be nice to have some sort of calibration or adjustment. I dare say if you want AMOLED then this will be a negative, but I'm fairly impartial and would say it's about on par with the S6. It's one of those things where you'd possibly only see any differences when you put the 2 side by side to compare.
Software:
It's not vanilla android if that's what you're after, but it's quite pleasant. There are some nice design choices for colours, the quick settings are in keeping with Material design and you can turn off some of the sliders so that it takes up less room at the top of the screen (take note Samsung!). The settings page is tabbed by default (you can revert to a standard list though) which is different to almost every android phone I've used and can take some getting used to. There's a few bugs here and there, hopefully these will be fixed in an update, nothing major though just a few niggles here and there.
Some reviews have said the Touchwiz on the S6 is better/more refined. Personally I'd say the LG UI is nicer, but this is subjective. I'd still prefer stock android, but most of the LG stuff can be removed or disabled.
Battery:
Only a day in, it's hard to say. But so far, not too bad. I was expecting it to be quite poor, but in reality it's ok. I'm down to 55% now, but thats with a lot of messing around with it and about 2½ hours SoT, WiFi and BT turned on etc. I don't have access to a quick charge 2.0 charger so I can't comment on that, I am going to see if I can pick one up though.
Camera:
I've had limited time to play with this, but from the quick go I've had it's seems as good as the S6 - I wouldn't say it was better though. Manual mode is way better than Samsung's Pro mode though, it's really nice to use and has all the settings you'd want. It also defaults to open in whatever mode you had it in last, which is nice as quite often it'll default open in auto mode on other phones. It takes about a second when the screens off to open the camera via the Vol Down shortcut. The only down side though, is that the camera settings don't appear to have any settings to change resolution? Not really an issue, but a bit odd.