One of our clients recently bought a bunch of iMacs 27", 5k retina, 32 GB RAM. Latest you can get from Apple as of today. They came with Sierra 3.
(Update to 12.4 did not bring any improvements).
On heavy layouts with lots of data and text he declared the performance being quite slow to unacceptable, compared to his old, non-retina iMacs 27".
We triple-checked the timings of all scripts and while operations like creating related records via buttons were faster in terms of milliseconds, the overall impression was a big slowdown. The script ended in 325 ms but the screen updated in like 3-4 seconds.
We got tons of mails along the lines of "this sucks", "wasting our time", "lawyers are on it".
Another client from a different part of the country bought 1 x of the same machine and expected stellar improvements but is right now terribly disappointed, as the 5k retina is the slowest machine he's got, where slowest is to be intended in the same manner: perceived, not measured.
After 3 weeks of losing sleep on it, I discovered a way to make these iMacs snappy. Which is disabling "Use LCD font smoothing when available" in the General control panel. Of course, the text has become less readable. (We use Calibri all over our solution).
Is this something people being in the same situation can confirm ?
Is this something that is going to be addressed in the new version ?