I just changed my previous Mac (MacBook Pro dual core running Snow Leopard) to a MacBook Pro i7 with Lion, and after it is still migrating after 3 days (and according to the migration bar is about 60%, even if it indicates since it started between 60 - 80 hours. I wasn't aware of the reboot with one key (guess T) to use firewire, so it is using wifi... It has been the worst nightmare I have gone through with a computer with any OS (yes, even Windows)
The worst thing is that the MacBookPro doesn't bring a CD/DVD so I could start the process on scratch usinqg FIREWIRE... and reinstalling the OS in case of any corruption. I don't know what to do, but, waiting another 3 days is going to be a big issue.