The iMac still comes in the unibody form factor Apple rolled out several years ago. The main iMac chassis is carved from a single slab of aluminum for solid, seamless, quality construction. The design is an instant attention-getter, and this iMac was a draw no matter who was visiting, regardless of technical proficiency. The silver of the aluminum and the black framed-glass remains striking; it's minimalism at its best, while still incorporating needed functionality. For instance, the deep black border around the screen hides the HD FaceTime camera and a green LED, which lights up when the camera is on.
The iMac has the same retinue of ports and wireless networking as before, with one very important addition: the inclusion of the new Thunderbolt port.
Thunderbolt was developed by Intel and implemented as the DisplayPort connection on Apple products. (If you've purchased a new MacBook Pro since February, that port you've been plugging your display into is a Thunderbolt port.)
The best way to describe the benefits of Thunderbolt is to compare its theoretical speed with current standards: USB 2.0 tops out at 480Mbps, FireWire 800 tops out at 800Mbps, USB 3.0 hits 5Gbps and Thunderbolt maxxes out at a theoretical 10,240Mbps, or 10Gbps. For every connection, there are two bidirectional channels that carry data over a 10Gbps pipe -- each way -- which means you can transfer a lot of data fast.
You can connect a wide variety of peripherals to a Thunderbolt port, from hard drives to displays, daisy-chaining up to six peripherals per port. In fact, it's possible to take a 27-in. iMac and flank it with two 30-in. displays, streaming multiple 1080p hi-def videos from connected RAID enclosures, without hiccups in the data stream. There are a number of real-world examples of how this works.
In addition to serving as a high-speed peripheral port, Thunderbolt can be used for Target Disk Mode and the new Target Display Mode. Target Disk Mode -- you have to hold down the T key while booting up -- has been around for years. It allows you to connect your computer to another one, with the Target Disk Mode machine serving as a hard drive. It allows for quick and easy data retrieval between machines, and being able to do so using Thunderbolt should speed things up considerably.
One more benefit: ThunderBolt is bidirectional, and with these new iMac models Apple has introduced Target Display Mode. In this mode, an iMac can serve as a stand-alone monitor, even if it's still processing tasks. Say you're exporting a large iMovie project using the iMac, but you want to use the iMac's screen as a second display connected to a MacBook Pro. With Target Display Mode, you can do that. This only works with hardware released this year.