Started copying about 39GB worth of various size files. Most of the time the copying notification window shows "0 B/s" for the speed and gives no time estimate. 

Sometimes it shows a speed that appears to be what would be expected. Right now it's been copying about 2,000 files ranging from 100KB to 2MB and hasn't shown a speed for several minutes. 

Other stats (total size, number of files and number of dirs) show correctly. But without the speed, there's no way of knowing how long it will take.

Reproducible: Always

Steps to Reproduce:
1.Copy files with Dolphin from one location to another.
2.View copy notification window
3.Press + to get more info.

Actual Results:  
Usually does not show current transfer speed, sometimes it does.

Expected Results:  
Always show current transfer speed and time estimate to completion. 

FWIW, This has been like this through many versions of Kubuntu. I always thought it to be annoying and hoped it would just get fixed or explained. But I've seen almost no mention of it, I can't be the only one. I've reinstalled Kubuntu fresh many times and still see this. Saw the same results using OpenSUSE not too long ago.

Right now I'm copying another 10GB of data, mostly small files (under 5MB). I can see both hard drive lights flashing away like normal, dstat shows expected transfer speeds as does iotop. 

I suspect this only shows the transfer speed of the current file. Which would make sense because the small files (under 5MB) copy too quickly to really display any useful info. If I try to put this infront of an everyday user, copying files is something I would expect them to do. Not often, but they will, and when they do they'll see 0 B/s but will see the file names changing and the other stats changing. They'll be presented with conflicting info, get confused and rather spend a few bucks to get Windows instead.  I know this is probably seen as purely cosmetic, but I think it's a Ux problem that should be either fixed or change how it works.