Should i upgrade to the D850?

I Already own the Nikon D750, and although I love the camera I'm very intrigued by the upgrades of the new D850.

A lot of times we photographers just want new "toys" whether we need them or not, so I'm asking…

Would even a great photographer notice a difference in image quality or performance going from the 750 to the 850?

Would you upgrade?

Absolutely

We have been using a Nikon D3s, D800e and D810 full frame cameras.

We have ordered two D850 cameras which will let us retire the D3s and one of our D810 cameras.

"Would even a great photographer notice a difference in image quality or performance going from the 750 to the 850"

Yes a working photographer will certainly see a difference, especially since the D850 has card slots for both XQD and Class 10, UHS-II U3 cards, both extremely fast cards. The D850 also shares the same autofocus system found in the Nikon D5 and D500, so accurate that even in low light, there's no need for an auto-focus assist lamp

Keep in mind that often when a photographer buys gear it's because of the way the camera works within the boundaries of their workflow.

You should buy the D850 if, and only if, your current camera is failing to allow you to capture the types of shots that you want to capture in the manner that you want to capture them in. A working pro has to think about workflow and how his/her gear affects their efficiency. After all, time is money. Which is why a working pro may prefer to use a camera with technically lower image quality than another. It boils down to making buying decisions based upon the needs of the client and their ability to produce quality images without sacrificing efficiency.

Therefore there may not be any discernable difference between the D750 and D850 to the human eye, but that's not as important as the camera's ability to allow the photographer to express their vision. Here's a link that allows you to compare the features of these two cameras: https://www.dpreview.com/...=pentax_k1

Under the Sample Images menu at dpreview.com, there's the Studio Comparison tool which allows you to compare ISO performance of various cameras. The D750 is listed, but the D850 is too new and isn't there yet.

Image quality, no improvement. It's mostly about you anyway. Performance? It depends on whether or not the new features really do help you shoot better or more easily. Would I upgrade? No.