Have you tried another way to migrate files such as Ethernet, Firewire, Wireless, or a Time Macine backup as suggested from the link you posted from ? Mac OS X v10.6: How to use Migration Assistant to transfer files from another Mac
I am using ethernet and it's been extremely slow. It's just now getting to 142 hours but last time it got that low it just jumped back up and both computers keep trying to go to sleep, both did while I was at dinner. I can't change it on the new one because I haven't gotten that far in the setup and I didn't know the old one would go to sleep while it was "working" Should I be concerned about it going to sleep. I haven't stopped it because I was told at the apple store that when it prompts you to data migrate to the new one is the only time it will let you migrate data to it
Don't allow the Mac to go into sleep mode.
Open System Preferences > Energy Saver
Move the Computer sleep slider all the way to the right
If you want to keep eye on the migration, same for the Display sleep slider
Deselect: Put hard disks to sleep when possible
You may need to click the lock icon bottom left corner of that window to make those changes.