Gotta love this stuff, here we are again beta testing sotware for the developers. Yes, I have found the same problem, I used the migration manager to migrate from another Plesk 9.2.1 software and it started working. I actually migrated about 6 domains, but then all of the sudden it just started hanging, a domain with only 20MB of date still hadn't finished after 50min., so I cancelled the migration. But of course that didn't stop the perl script from running on the machine that I was migrating from, even Kill PID didn't work, so I had to reboot the server. Tried several more times with several other domains only to find out that apparently there must be a limit to how many successful migrations you are allowed because it never worked again;-)
So it was time to try the command line backup/restore hoping that it might actually be fixed. WRONG! Ended up with map problems, so I followed the 9.2.1 backup CLI manual and manually created map files, only to find out that when you follow the steps you end up with a message from pleskrestore that it has been deprecated. So I looked in the KB and decided to copy backup files from the old FTP repository (oh yes, Plesk still does not allow you to copy a backup file from an FTP repository to the server repository or delete an FTP backup either) to the new server and actually try to restore it from with Plesk. But I found that it restored a 656MB file in about 5 seconds, and discovered that it restored the databases, with no tables, the base web structure, with no files, email accounts, with no emails. But the good news is that it reported that the restore was successful (not sure in who's opinion). No wonder it only took 5 seconds to do a restore.
Plesk 9.2.1 (beta), CentOS 5.3 64-bit, PHP 5.2.9, MySQL 5.079