Good afternoon!
I've got one problem with Dolphin for a very long time:
After some time it(and it's windows) begin starting/opening more slowly in KDE. It's very big problem for me, so after some time from installing of any system with KDE I need to change system or change desktop environment.

More info: full start of Dolphin is about 6-8 seconds, his windows( like "Delete file?" or "Apply changes?" and etc) are opening about 3 seconds. So in sum this make working with files very slow, especially when I need to find/get any file quickly.
My PC specifications:
OS: Any OS with KDE
CPU: Intel Core i3 (2 cores, 2.4GHz)
GPU: NVIDIA GeForce GT 540M (1GB)
RAM: 8Gb

But my friend has the same specifications(just with 4Gb RAM and AMD GPU - 1GB) and he hasn't problems with KDE.
I've heard that OpenSuse is more optimized for KDE, but problem with long start/open was not disappeared.

Testing on Maui with latest KDE (for 9th of march of 2017):
https://youtu.be/QoQBbWrtxhk

Full report from strace Dolphin: http://pastebin.com/cRRFiT0k
Full report from dmesg Dolphin: http://pastebin.com/YQ7u5FQ5