I would like to add my thoughts. I use DOpus at home from an SSD in my PC. At work i use the USB export. And i use DO a LOT! 8 hours daily at least. From my experience:
Some things really slow down DOpus, like opening the toolbar config menu, resizing the window (i have lotsa custom made toolbars), sometimes scrolling with a lot of files selected (by a lot i mean 300+). For example, when i need to configure a toolbar, i right-click, click on customize, now sometimes i have to wait a few seconds, the toolbarconfig opens, then edit a button, then OK (for the button changes), OK (to close the toolbar config) and lotsa times if i dont wait between the OKs, the changes i made to the button do not show up, nor save. Or when i resize the whole window it stutters like in the video @Pear has posted.
Thougths: for the window stutter, i accept it because i think the system tries to redraw a lot of toolbar elements at once. As i said i have everything customized to the teeth. For the slow config opening and saving, i think Windows itself is either scanning the USB drive, thus the saving of the config sometimes works, sometimes doesnt. I think its more the porblem of the OS than DOpus.
On the 8GB Datatraveler USB: DOpus, 500 icons, 20 mp3 files, 378MB of apps, like ffmpeg, foobar, 7zip, nothing too resourcehoggy. Tried on WIN10pro 64 (home and workplace) and WIN7enterprise 32 (workplace)
The config thing and others are fast as they should be. The window resizing is still stuttery, i dont know why, i have a GTX650TI nvidia card, i think its Win10 again, maybe something in the method it redraws all the toolbar elements.
On the PC its WIN10pro 64, default antivirus, everything default, fully updated. Default drivers offered by windows, i only play games and manage files, watching movies and listening to music.
So i also experience the things @Pear does, but i could live with them, they do not conflict with my working experience, but looks like its not just me. At home i have an AMD cpu, Gigabyte motherb, GTX650TI (something like a 4-year-old computer) and i maximise power usage, no battery saving stuff, no USB sleep and any other thing. So i just wanted to tell you that @Pear is not the only one with these issues.