I've been waiting a lot for my computers.

I have a bunch of video files on my Mac. When I select one in the Finder to open it, I first have to wait for ~3 seconds with a spinning cursor while Finder generates a thumbnail preview. I don't want a preview, I just want to watch the video.

On my Windows box in Zürich I have an SMB mount to a fileshare in California. I expect it to be slow, it's a long way. But it's slow even when I don't use it. I'll sometimes accidentally drag a file across the remote folder icon on my desktop. At that moment Windows decides it has to query the server for a bunch of stuff, forcing me to wait.

Applications should not force me to synchronously wait for some action I don't even want. Do the work in the background or substitute a low fidelity fast operation.

Then again doing that wrong can be a hazard too, as Picasa and iPhoto show. When browsing photos full screen, both apps first show you a low-res version, then 1–2 seconds later swap it with a high-res version. I assume this is a choice to make the app seem more responsive (less waiting!), but it's really just obnoxious because of the visual distraction.