The Power Mac G4, introduced on August 31, 1999, was the first traditional desktop design for Apple during Jobs' second run with the company. It was also one of the first Apple products credited to its now Senior Vice President of industrial design, Jony Ive. The PowerMac G4's sculpted plastic handles and friendly-future styling were a welcome departure from the sea of beige towers on the Windows side of the aisle.
Apple introduced its most innovative design, the Power Mac G4 Cube, on July 19, 2000. While this system was not a mass market success like the iMac G3, it remains an iconic example of millennial-era consumer product design. You'll find this system on exhibit at the Museum of Modern Art in New York.
The PowerBook G4 was the laptop design that arguably put the largest aesthetic gap between Apple and its Windows-based competition. Where the rest of the market was mired in a seeming random selection of dark-colored plastic, Apple's aluminum and titanium iterations of the PowerBook G4 turned the laptop into a fetish object when it was introduced on January 9, 2001.
With the Power Mac G5 (a June 23, 2003 debut), Apple's standalone desktop line shed its roots as a consumer desktop and essentially became a professional workstation. The all-metal exterior echoed the serious industrial design of the PowerBook G4.
The iBook G4 (October 22, 2003) merged the approachable plastic finish of the iBook G3 with the clean-lined aesthetic of the PowerBook G4. This laptop brought a refined look-and-feel to Apple's consumer-oriented products, and also hewed closely to the design of Apple's now 2-year old iPod.
Introduced in August 31, 2004, the iMac G5 signaled Apple's clear separation from mainstream Windows-based desktop designs. Not everyone was convinced of Apple's insistence on a closed hardware for general purpose computing, but it was hard to argue with the sheer visual appeal of the updated iMac.
Apple introduced its aluminum and glass iMac on August 7, 2007. This system, as well as the unibody update it introduced in 2009, extended Apple's industrial design leadership from the PowerBook G4 and the PowerMac G5 to its all-in-one desktop line for the first time.
The Windows market is only now making an industry-wide attempt to challenge the slim-and-trim MacBook Air that Apple introduced on January 15, 2008.
At the time of its debut, the MacBook Air was expensive in part due to its dependence on relatively new, and expensive, solid-state hard drives. Although it seemed like a vanity product at the time, the MacBook Air and its absent optical drive were one of the first signals of Apple's intentions to free computer users from physical media in the same way the iPod and iTunes liberated music fans.
Apple's unibody MacBook and MacBook Pro (October 14, 2008) designs were the first true conceptual laptop update since the PowerBook G4 from 2001.
The seamless aluminum body and edge-to-edge glass display carried over and refined the metal and black plastic design Apple introduced with its aluminum iMac in 2007, extending it to both the high-end MacBook Pro, and its more mainstream MacBook laptops.
The Mac Mini received its last true design overhaul on June 15, 2010, with a unibody aluminum chassis in the same vein as the most recent iMac, MacBook, and MacBook Pro. In recent updates to the Mac Mini, Apple has added HDMI output, allowing you to more easily use it as a living room PC, and also shed the optical drive as with the MacBook Air. Both steps suggest Apple's ongoing effort to ween customers from physical media, and encourage them to acquire their media and software from Apple's various digital distribution services.