Desiv summed a lot of it up. For myself:
Datatypes: allowing old software and the OS to use the latest formats, great idea.
Public screens: A bit like linux workspaces.
Fast multitasking: I know it has it's faults, but it works very well for me
RAD and RAM
well organised: Everything has it's place, and you can explain to a layman how the OS is organised in 5 minutes. Unlike the mess a windows folder is as soon as you install windows.
Fits a lot on screen: seems higher resolution than it is.
DosDrivers: A great way of adding new filesystems, again, easy to understand.
startup-sequence: I know it's not drag and drop, but it's easier to understand than the registry.
WBstartup: no hunting around for what the hell is bogging your comp down on startup. Check WBstarup and S: and your done.
Low resources: Does not need two gig to get out of bed in the morning
Fast boot time: each PC I get boots slower than the last, despite being much faster ( I guess HDD speeds have not kept pace with data needs?)