In my day to day activities I often encounter a wide variety of User Interfaces.
Some are really ugly and almost impossible to navigate easily. Simple things like entering dates can provide a level of frustration that makes me want to throw things at the screen. Some have menus with annoying hover "capabilities" that I'm sure looked cool at design time, but when you're a microsecond too slow with the mouse cause nothing but hassles.
Some aren't too bad, but I can't think of any that make me go "wow".