Meh - my Mom's iMac has the 2TB fusion drive and it works surprisingly well. When I dual boot it into bootcamp with Windows you can tell the SSD caching is not there; it's pretty obvious. Sticking a 32GB SSD (formatted NTFS) and dedicating it to readyboost helps a bit, but it's still no where near as effective as fusion under Mac OS. Obviously being pure SSD would be better, but when she got it almost five years ago that much SSD - even third party - would have been cost prohibitive and it's still pretty expensive to get 2TB as all SSD.

I’ve been very happy with the 3TB Fusion drive in my 2014 27”, it’s hugely more performant than a bare hard drive. I’ll probably be getting a new one with a 4TB SSD, but that will make the new machine over a grand more expensive than my old machine was. These new SSDs had better be zippy.