Another key issue is "perceived performance". I have worked on a number of systems when the performance has been drastically improved over the original system, however, the users disagree. This has at times lead to management support for the users belief that the performance is worse.

Whilst I do agree with management support for users opinions, it is important for IT professionals to fix real problems and resolve perceived ones. For performance this is achieved through measurement. Just by sticking to the facts you can be deemed as being helpful. It brings clarity to the situation e.g. showing that the users' claim that it is taking twice as long is inaccurate but accepting that it is 20% slower and agreeing (before being asked) that this is unacceptable is helpful.

I guess the key thing is to try and be the voice of reason and take the emotions out of the situation. Publicly support the possibility of the perceptions then prove or disprove them. Don't bother counter the claims but lead with the results from measurement. If there is a performance improvement but it is being reported as a fall then offer the facts and ask if there may be another reason.

I guess it boils down to what Douglas Adams told us all: Don't panic!!!