Upgrading/Moving from one computer to another is always painful and usually the only thing that makes it worthwhile is if you're moving to a newer, much nicer, machine. I recently got a MacBook 13.3" (3 weeks before the pro was released, sad) and have been living partially on that. My tower, Mac Pro, has been feeling somewhat neglected. My wife has been doing more video editing lately and needed something a bit faster. I decided to give her my tower, gulp, since I haven't been using it much anyhow.
I was already partially up on my laptop so it was just a matter of copying over any remaining items. After this was done I did a fresh install on the tower. I've seen the 'MIgration Assistant' application before but had never really given it much thought. I had made the basic assumption that it wouldn't do exactly what I wanted and there would be a bunch of manual intervention as well. I had installed the new Snow Leopard on the tower while her old laptop was running the previous Leopard. I decided to give the Migration Assistant a try, expecting a lot of additional work afterwards. I hooked up the computers via Firewire and started the Migration....
The assistant started up and located the old mac right away. Then it searched through it and gave me a check box list of items I could move/leave. I left everything default and let it run. My wife has our whole family album all digitized in iPhoto, about 130 Gigs not including videos, so you can imagine that it did take some time.
Once this was all finished I was very surprised by the results. It actually migrated over her user from the old computer. It kept her login items, login image etc. It even set her wallpaper to what it was before with all the same settings. Screen saver was the same, along with settings. "That's pretty neat" I thought as I opened up iTunes. Wow, iTunes kept everything just as it was on the old machine, ratings etc. Next I opened up her email. All her emails where setup and it even moved over her existing inbox emails! Her calendar kept all her events and so did Address Book. Then I looked down in her application bar. It was setup just as it was on her previous computer. It even moved over applications that hadn't been installed yet!
When everything was said and done the only thing she noticed after the move was that her computer was faster. There was nothing else that she noticed different from the day before.