The original 520ST case design was created by Ira Velinsky — Atari's chief Industrial Designer. The ST was basically wedge shaped, featuring bold angular lines and a series of grilles cut into the rear for airflow. The keyboard had soft tactile feedback and rhomboid-shaped function keys across the top. The 520ST was an all-in-one unit, similar to earlier home computers like the Commodore 64. By the time the 520ST reached the market, however, consumers demanded a keyboard with cursor keys and a numeric keypad. For this reason, the 520ST ended up significantly larger than previous popular all-in-one machines like the Commodore 64.
The 520ST used an external "brick" power supply, floppy disk, monitor and mouse. Even basic system setups thus suffered from cable spaghetti, a problem future versions would address to one degree or another. Early 520ST owners became accustomed to the "Atari Twist" and the "Atari Drop" service procedures. The "Atari Twist" seemed to help discharge built-up static electricity (Atari soldered-down the metal shielding to fix the problem) while the "Atari Drop" appeared to help re-seat chips which may have become partially unseated over time.
Source: Wikipedia, "Atari ST", available under the CC-BY-SA License.