Hey all,
I have to say macrumors does a pretty poor job of documenting various Dell issues, I think various Mac issues with various Rev's/models of these monitors should have been documented, by the way, Dell no longer supports OSX, so try to stay away from these monitors
Let me contribute
P2415Q, Rev A01, Latest Yosemite, Startech Cable: (from Amazon UK)
Whenever the monitor wakes from Cold Sleep, the MBp adopts all the windows, then offloads it to the external monitor, so every window is resized and messed, it's annoying beyond imagination yet liveable with, used to happen 20% of the time, now it happens 100% of the time
My Dell U2413 used to freeze occasionally, don't wake up from sleep, this monitor also has that issue, yet with a lower frequency, I would say 0.5%, while the Dell U2413 was almost 5%
I have a keyboard macro that re-enlarges windows, but still, it's annoying, and some webpages can't recover from this resize (Tinkercad)
I try various settings with each monitor, hoping one fixes these issues, yet none does