There is no way to 100% determine whether the RTM is different from SP1 RC Refresh 2 which almost no one has except Microsoft Connect testers. We are sure that the files we had up are from Microsoft. Its possible they released SP1 RC Refresh 2 as the RTM if there were no major bugs found. As we stated earlier the new Windows Automated Installer Kit references the final version of Vista SP1 as Build 18000. "Build 18000" is an external even number for the RTM build.

6001.18000.080126-2040 - > Refresh 2 and probable Vista SP1 RTM