Yesterday I upgraded my S3 with a seagate 750gb sata drive. It was fairly painless and took about 2 hours altogether.
I used the guide found here –> [url=http://www.engadgethd.com/2006/10/26/how-to-upgrade-your-series3-drive/]http://www.engadgethd.com/2006/10/26/how-to-upgrade-your-series3-drive/[/url]
Followed it word for word, except I used an onboard sata controller.
I now have the ability to record 100 hours of HD programming or up to 900 hours of SD.
Not sure what I am going to do with the old drive, probably keep it around for a few weeks to make sure I don’t have any problems.