Always reinstall Mac OS X using the included discs and do NOT rely on the version installed at the factory.

Why?

Often I have experienced strange issues when relying on the factory installation, such as broken applications, file permission errors and other odd behavior under the hood.

My hunch is that the disk imaging system in the factory may contain older, less polished versions of Mac OS X than is shipped in the box.

Voodoo or superstition?

Could be! But experience with dozens of Macs taught me that spending the hour up front helps avoid issues later.