The previous line of iMacs had a base model that came with a 500GB, 7200 RPM drive. The new line of iMacs has a base model that comes with a 1TB, 5400 RPM drive. What a bummer. This is all according to the 'tech specs' page on the Apple Store website. In addition, it appears that the "fusion drive" isn't standard on any of them and will be an upgrade. Any speculation on how much you think this upgrade will be? Given the slow speed of the base model's HDD, you pretty much have to upgrade that thing if you want to utilize all the new performance (and eventual benefits that come with a maximum of 16GB of RAM).