I just did this.
And it worked great.
Took about 3 hours to transfer 18GB.
I spent all morning trying to hook my two empegs up via ethernet, USB, etc. Tried using the empegclone tool (a miserable failure) and the clone option in jemplode. Looked into the lazy bastard guide but got scared and chickened out.
Finally found Rogers super basic instructions and it worked peachy. Easy to do, even for a totally linux impaired nitwit like me.

Just for future reference...

It's even quicker if you've got a PC available and a laptop IDE adapter. You'll need a Linux boot CD though (Knoppix will do) to run on the PC. Run the builder image on the new drive. Plug both drives into the PC. Mount both music partitions and copy away. Unmount the partitions. Shutdown the PC and install the new drive into your empeg. This is if you're comfortable with Linux and okay with moving all the hardware around.
I just plugged my old 20GB and my new 60GB into my server and copied the files straight over.

- Trevor

And it worked great.

congratulations