Comment by flysand7

UI feels unresponsive. You click a button, and the button doesn't seem to do anything. In case of the left-hand side buttons, it it's just a lack of response from buttons that's unsettling, but on the right side its worse because there's zero action happening on the screen until the new background finishes loading and applies itself to the screenshot.

I would probably add some animations to make UI feel responsive. Something like make buttons highlighted on color / have a color animation after click, and have the application properly tell you when its loading something / the requested action is in progress.

I would also mention there's a very slight delay (60-200ms) between clicking a button and the thing happening on screen, but I guess that's average web application experience nowadays... so I won't complain