I recently picked up one of the new MacBook Pros to replaced my older model.I migrated everything pretty easily with Migration Assistant, and other than having to re-authorize a lot of programs, it was pretty painless. I connected my old laptop up and booted it into Firewire Target Disk mode, then ran a firewire 800 cable between the two laptops and let it copy away for a few hours.
Of course, I have an external backup drive that I use once a week to protect the system. I also have a Western Digital MyPassport Studio USB/Firewire 800 drive that I use as a portable backup. I don't back it up as often, but the idea is to have an emergency backup drive on the road should something happen.
Well, I hooked that drive up to clone off the internal to it, and something odd happened. The backup froze up after only a couple of minutes. Super Duper was stuck, and I had to force quit the program to get rid of it. I couldn't eject the disk, either – it was obviously hung in some sort of I/O operation. So I pulled the cable out and got the nastygram from the system about properly ejecting drives. Putting it back in showed the drive had an invalid partition. Great. So I re-partitioned the drive, and even that operation hung. So by now I'm thinking I have a bad disk or bad controller. I really don't want to take this apart, because once you do, many of these Western Digital cases don't go back together.
Instead, I take the drive over to my MacPro and repartition it. It works fine in a few seconds. Then I copy one of my disks with around 200 GB of data. It takes a while, but everything copies fine.
Now I'm hoping it was just a bad partition and I take it back to the MacBookPro. Nope, it hangs after a few seconds of writes. So then I remember that Western Digital provided some drivers to get more speed than you get normally from the OS X standard drivers. So I load up the drivers, reboot and – the disk still hangs.
So I finally try something I should have tried much sooner – I use the USB connection. Yes, it's much slower than Firewire 800, but guess what? It works. The drive has been cloning for a couple of hours without a hitch. Since newer MAcs can boot from USB, it will still be a good emergency device. But I'm certainly disappointed that the Firewire portion doesn't work. It's been a few years since I ran into a Mac upgrade that had a firewire compatibility issue.
So what's my point here? Well, one is to not overlook the obvious. I had actually forgotten at first that the drive did USB as well as Firewire and came close to dumping it. Only after it copied fine on another system did I have any confidence in the drive again. If I had just hooked it up via USB as soon as the Firewire failed, I'd have narrowed down the problem a bit (and gotten my drive copied a few days ago when I first tried). After getting a good copy I could have done some more experiments.
The other point to keep in mind is that not al your peripherals from an older system may make the transition to a new one, so be prepared to replace some of your peripherals if need be. If there is some device you can't do without, make sure first that it works or else be ready to purchase a substitute (or skip the upgrade).
Third, if you have one of these drives, you'll have to switch to USB at least for now. I'll be submitting a bug report soon but who know if and when it will be fixed – since it seems to be a hardware issue, and not just a driver issue.