I am currently in the middle of testing and app and web site. Because the software is on a test server the response rate is slow (at least I hope that is the reason).
It was great timing that the the latest edition of Jacob Nielsen's usability newsletter was published and it is all about how to indicate to the user they have to wait.
My concern was that because of a delay the user will get impatient and click twice (the sort of thing that I do).
According to the usability guru, the last thing that you want to do is say "don't click twice". Why? Because people rarely read the text - I am sure he is right.
The more I think about this issue the more interesting and important it becomes for all ages of users but particularly for oldies.
If you are involved in the digital pond then worth a read. Dick Stroud