iMac Pro update... It took me a while, because I screwed up a couple times, but I now have successfully moved my entire working environment over to my new iMac Pro. I'm using it exclusively when working at my desk (on bills, at the moment). What's it like? The short answer: fast!
The only compute-intensive thing I've tried so far is OCR on scanned documents, and (quite predictably) that's very fast indeed, especially when there multiple documents queued up. But other things are also notably zippy. For instance, Firefox with 60 or so tabs isn't noticeably slowed down at all. I'm sure that's basically because of the insane amount of RAM in this machine. At the moment I'm running with 16 GB of RAM used (out of 128 GB). The OS isn't even thinking about swapping :) That's something I do every day (the tons of tabs), and that zippiness is most welcome.
Just playing around, I've loaded up both Chrome and Firefox (simultaneously) with 100 tabs. Both of them are just as fast as they are with a single tab. Woo hoo! My development tools (Jetbrains' suite) have lost any noticeable lag in anything I tried (on the laptop quite a few things have noticeable lags).
Nothing I've done so far has caused the CPU to even break a sweat. The CPU consumption graph looks like a flat line at zero. I haven't heard any fans in the iMac, though I know they're present – I'm actually not sure whether they're just really quiet, or I haven't worked the machine hard enough for the fan to be required. I haven't done anything that's working the GPU hard, either.
The three screens are magnificent to have available. I'm experimenting with layouts. Right at the moment I've tiled my right-hand screen with email, messaging, and iTunes; three things I'm constantly using. My left-hand and center screens are for my work - plenty of screen real estate for anything I do.
My this is nice!