aaaaand so it begins
downloaded and installed iphoto 9.6.1 - error message - iphoto needs to be updated to the latest version (which 9.6.1 is).
run software update - no later version available.
i then discover that the very latest updated version of yosemite will not accept any version of iphoto, only option is to downgrade yosemite to an earlier version.
so, i figure i'll boot the machine from a clone backup i took of the drive prior to the mavericks > yosemite upgrade, thinking i'll run iphoto from there and copy the various albums / folders to a different ext drive, boot back into yosemite and allow photos to create a new library and import the various album folders.
boot into mavericks from the ext drive.
try to run iphoto - error - iphoto needs to be updated to the latest version.
run software update > no update available.
download iphoto (various versions from between 9.3 and 9.5.2)
delete existing version of iphoto and try install 9.3 - error message, iphoto needs v9.1 to perform this update.
remove all traces of 9.3 and install 9.1, try run it - error message - iphoto needs latest version . . . .
run software update - no update available.
essentially, when trying to have photos import the existing iphoto library, photos gets to about 10%, freezes, and throws out an error message regards permissions.
i have run disk utility on all drives, verifying permissions - no errors.
i also saw a post somewhere advising setting permissions on the ext drive containing the iphoto library to "ignore ownership on this volume"
alas - nothing helps