Got my new 120GB Xbox 360 drive today. Ordered it from Amazon on Thursday, 27 November 2008 and received it promptly today. Cost was $135 and shipping was free. Can't say enough how much I love Amazon.
Before I did the transfer, I wrote down all the Xbox Live Arcade games and 360 theme packs I had downloaded to the old hard drive.
The transfer process went pretty smooth. Basically you turn on the 360, hook the transfer cable to the new drive, connect the other end to the USB port on the back (must be the back USB port) of the 360, insert the transfer CD and start up the CD (I have CD autorun turned off on my 360). The software runs you through some prompts and then begins.
Remember that this process is irreversible. You can't move the games and data from the larger drive back to the smaller one, once the transfer has completed.
Once the transfer was done, I did a check and found that all my Live Arcade games were still there as well as the themes I had downloaded or purchased.
The only other cleanup I had to do was to get rid of a bunch of demos and videos that Microsoft preloaded on to the larger hard drive.
Total time for transfer was about 1 hour 20 minutes or so for 16GB worth of content including cleanup.
No additional steps were required to transfer licenses or anything. The whole process was about as easy as it gets.