When adding an 8 entry into the 7 BCD the CP seemed to run well. I had to use the newer Automatic repair option that replaces the Startup repair to rewrite the 7 host drive's mbr and boot files. Later when going to run the RP as a stand alone on the second OS drive I ended up using the PC Refresh option which automatically added 7 in. Both OSs were trashed due to the subsequent booting into 7 when selecting 7 from the 8 boot options.
Fortunately I was a little overdue for a clean install of 7 at the time and simply wiped both drives! First however once both froze up solid when going to start each the Disk Check tool bailed 7 out but 8... lingered a bit. Then when going to switch from Native ide mode to AHCI 7 automatically adjusted itself reinstalling the two OS drives as SCSI devices while 8 was history!
So much for the dual boot and RP install. A small portion of the second was set aside as the root and swap partitions for Linux to try out 7 and 8 VMs on the Linux flavor of VBox where the 7 install took but not 8. The RP on VBox is still going on the 7 host following the clean install of 7 as the last look so to speak.
The Enterprise 90 day for developers based more on the RTM will have a fast look there if it succeeds to install on VM or replace the Linux distro on the second drive "when i get to it" that is. With 8 unlike 7 and Vista before it this is one version I will be "taking my time" with!