I personally have migrated many Mac hard drives before.
Carbon Copy Cloner is great, but personally I prefer booting from the OS DVD and use asr on Terminal.app
This is done with the new drive in a cheap SATA-USB HDD case plugged into the Mac.
Basic example of the asr command on Leopard.
asr restore -source /dev/disk0s2 -target /dev/disk1s2 -erase
This will clone disk0s2 which is the existing internal drive to disk1s2 which is the external drive.
Use the command "mount" to determine the drive name of the external drive.
And at times where the hard drive content is huge, and I do not have the 3 or 4 hrs to wait, I'll use the -noverify option like in this example.
asr restore -source /dev/disk0s2 -target /dev/disk1s2 -erase -noverify
This will skip the verification after the restore process is done, cutting the time to about half.