I tried to transfer my wife's files from her MacBook, running 10.8.4 to my MacBook Pro running 10.9.5. We have identical logins on both computers.
I was using Migration Assistant on both Macs which are on the same local network.
I got the following error message:-
The selected source cannot be used for migration. Your other Mac is not running the latest version of OS X. Please run Software update on your other Mac and try again.
I don't want to "upgrade" my wife's computer, just transfer her user files. It seems pointless that you can't migrate from an old Mac.