I suspect that if we paint a picture, in very broad brush strokes, of the two camps arguing the for and against, it probably boils down to those that always liked the GS for its character, and those that were always slightly frustrated with its (relatively) poor performance.
I get the 'experience' thing. I understand Dainese Brave and Davey F when they talk about the new bike loosing some of its character, becoming a bit more Japanese ...
But there will be many (and I very much put myself in this bracket) that will be saying 'Ahhh .. at last .. the GS I've always hankered after ..
now it's got a bit of performance .. a bit of get up and go .. '
For 25 years I've had Japanese bikes. From Track bikes to dispatch bikes to tourers. Before my GSA I had a Pan 1300 (nestled next to zx6 track bike). The Pan was a beautiful bike - lovely motor - that V4 on full chat on a fast flowing smooth A road was just a delight. But feck me, what a bland fridge of a bike! And it was that! Ultra reliable, did exactly what it said on the tin, and ultimately I got rid of it, because it was so bland and boring.
I liked my GSA when I got it, I 'got' the Davey F experience, I quite liked all it's little character traits, its burping and wheezing, the vibey mirrors at the lights; I can completely see why somebody like Andres had a Guzzi.

eek ..

). But for me and, I'm guessing, my camp, the one thing it missed was just a bit of a rush. You could tick all the off road, touring, tiny b road bimbling / hooning, but sigh ... it just didn't have that braap, braaap, braaaaap ... 140 about it!
I like this new bike. Yes, it's lost a bit of character. But bloody hell, it still isn't a Japanese fridge. So to me, it's a good balance of what I have been looking for in a bike at my time of life; a bit of character and a bit of performance.
There will be many many people like me!
And there will be many many people like Davey F, that are now missing the Je ne sais quoi, that the traditional GS had in spades and that this bike is just slightly missing ...
So it's horses for courses. You can't please all of the people all of the time.
(But I'm right and Davey is wrong ...

)