Good point haku.
Yes it could well be a gratuitous step to perform. Depending on, of course, what you are processing the server should handle things with decent speed making this step unnecessary. Even the processing of Credit Card data via a 3rd party payment gateway usually only take a few seconds at the most.
If you were performing cpu hogging processes such a zipping a large data file or something then I could understand the holding page might be useful. Or even perhaps showing the status of a mass mail-out or anything along those lines where it would be beneficial to the user to see the status of said process.
Hopefully this will have given you some idea's on how to code or why to display or even if this step is justified.
- Mike