I too used SuperDuper! with Tiger but as soon as I got my hands on Leopard, I started using TM. Why? Well, it's automatic. Problem with SD! is that I would forget to plug my external HD sometimes and the backup would not go through. You can enable to backup TM to a HD attached to AirportExtreme (with a small hack) so that's my makeshift TimeCapsule and works well because I don't have to remember to do anything.