If you want faster drive speed, as well as zippier startup and application launches, the new $1499 21.5-inch iMac can be outfitted with Apple's 1TB Fusion Drive. Fusion Drive combines fast flash storage with high capacity hard drives and presents the two as one drive to the user and software. The OS and all applications that come with an iMac are loaded onto the flash portion of the Fusion Drive, making application launches and restarts much faster than with a standard hard drive. In our testing, we found that most tasks on a Fusion Drive perform at the same speeds as a stand alone solid-state drive, even with 600GB of data loaded onto the drive. Long extended writes and reads will eventually hit the bottleneck created by slower hard drive speeds, as you'd expect. Previous testing showed Fusion Drives able to finish our 6GB file copy tests in about 40 seconds, while the 5400 rpm hard drive in the iMac took around 150 seconds to complete. Fusion Drive is not available on the $1299 model.
The new iMac steps into the future, with cutting-edge design (literally), updated processor and RAM, better sounding speakers, and reduced-glare (but still glossy!) screens. Unfortunately, the new iMac also follows Apple's trend towards less repairable and upgradeable Macs and the elimination of useful features such as optical drives and FireWire 800 ports. I think it's reasonable to drop the optical drive from laptops, where the benefit of reduced size and weight can be immediately appreciated when you walk around with a laptop in your bag. On a desktop computer like the iMac, it's unclear what the benefits are of going without these conveniences in order to have a thinner and lighter iMac at your desk--unless you're admiring the iMac from the side, of course.
The $1499 iMac benefits from a Fusion Drive upgrade to Fusion Drive and Core i7 processors--something you can't do with the $1299 iMac.