The reason for the recommendation to wait before removing the SP1 installation files is to ensure there are no issues. Just because everything seems fine immediately after installation does not mean that there are no issues with all installed software on the computer. people have tested all the programs on their computer.
At this point there are only two known programs that do not work after the installation of SP1 and two that lose functionality after install. That is not to say that the list could not grow as more people install the service pack. Should such a program be "business critical", not having the ability to uninstall SP1 could cause a hardship.
As to your situation, mjf, no, I do not think it is necessary to re-image and reinstall SP1.