Hi Peter,
I bought a new 2017 imac 5k - i5 processor, 1tb SSD, 32 gig ram, 4gb VRAM.
Very nice machine to replace the aging macpro tower in our photo studio.
I’ve hooked it up to a Synology DS418 with 4x4tb drives for storage.
Works very well.
Use it all day every day running PS CC 2018, bridge etc.
Handles my Astro files well too which are sometimes up to 2gb in size with all the layers.
Speed is fine for stills. I don’t do video so can’t comment there.
Didn’t see the value in an iMacPro for the same reason - it’s performance boost is really designed for video/movie makers, and it’s staggeringly expensive!
The screen itself is an amazing thing of beauty!
Movies, browsing, youtube etc are a pleasure to view.
BUT.....
Can’t use it for photo editing- looks great but it’s too contrasty and you can’t adjust it.
So I run a second, calibrated monitor off it, which runs nicely at industry standard.
It’s a shame that Mac abandoned development of the MacPro, but this combo is a decent, workable replacement.