Migration Assistant - 3 Computers?

Question

Hello all,
I have a question regarding the Migration Assistant process. So, before I get into the problem, let me identify all three of the computers.
PowerPC iMac with iSight - No longer works, but has the most important account on it. We are getting a computer repairman to migrate the account from this computer to the second computer at a later time.OS: Most recent version of Leopard
Mid-2010 iMac - Was bought used, but the computer should be empty. This will be the "host" computer. We want to move all of the accounts over to this one.OS: Most recent Snow Leopard
Early 2007 iMac - This computer is working, and has THREE other accounts we want to move over to the host computer. However, they are less important than the one account on the PowerPC. OS: Most recent Snow Leopard
My concern is that if I were to migrate the accounts from the Early 2007 iMac over to the host iMac today, and our computer repairman came out later to move the account from the broken iMac to the host computer, would there be any kind of reset needed? I want to make sure that the accounts on the 2007 iMac can be moved over to the host iMac without conflicting with the account on the PowerPC iMac.
Also note that the PowerPC won't boot for longer than 30 seconds, so I imagine there must be a complicated procedure involved in moving the account over to the host computer. This account on the PPC would be the primary account.
Finally, I did note the Migration Assistant patch updates from Apple for Leopard and Snow Leopard. I plan to install the Snow Leopard one to the 2007 iMac today. Will the Leopard one be needed on the host computer though?
I hope I was specific enough... if you need any clarification, please let me know. I will reply as quickly as possible. Thank you for your time!
-Justin

Answer 1

You can run Migration Assistant as often as necessary, so you should be able to migrate all the user accounts you want, in any order you want, with a couple of restrictions:
It will not "merge" any accounts; each will be transferred separately, so it sounds like you'll end up with 4 or 5 different user accounts.
It will not transfer an account with the same "short user name" (same as the home folder name) as one that already exists.  It can, however, rename one of them and continue the transfer.  See the last sample in the pink Migrating User Acounts box of Using Migration Assistant on Snow Leopard or Leopard for details.
As you'll see in the pink Migrating Applications box there, it won't transfer apps that already exist (with the exact same names in the exact same locations), so as long as you start with an up-to-date version of Snow Leopard, you'll keep the default Snow Leopard Apple apps. 
Other Apple apps, such as iWork and iLife, and 3rd-party apps follow the same rules; so if you elect to transfer apps, and have different versions on different Macs, be careful to do the most recent ones first.  If in doubt, you may want to un-check the Apps box and reinstall from the original discs.
Your best bet will be to start the new/used Mac from a Snow Leopard Install disc (either the one that came with it or a Retail version), erase the internal HD, and install OSX.  That way, you'll be sure there aren't any nasty surprises left over from the previous owner.
When it starts up again, use Setup Assistant to do the first set of transfers, not Migration Assistant.  (See Using Setup Assistant on Snow Leopard or Leopard.)  That will reduce the number of user accounts you end up with by one, and possibly avoid some of the things in Problems after using Migration Assistant