I just can’t get over how many product managers there are who seem to think that it’s okay to release products that don’t have responsive UIs. If a device locks up for a few seconds when I press a button, you’ve failed. If I get some feedback a few seconds after I push a button, you’ve completely failed.
It is really important for the user experience that every time a user does something to interact with your tool, _something_ happens immediately. If that something is a notification that the machine needs to think about it for a while, that’s fine, but make it abundantly clear that the user’s input was understood and processed. It is not okay to just leave the user hanging.
Particularly, I’m stunned at how many recent cellphones suffer from this problem.