Looking at implementing a split-button similar to: the jQuery SplitButton demo.
Whats the difference between this example and just using 2 buttons? am I missing something?
..particularly regarding the joint "set" demonstrated...
That's all it is: two buttons that are grouped together. As it states on the webpage -
An example of a split button built with two buttons: A plain button with just text, [ and ] one with only a primary icon and no text. Both are grouped together in a set.
They were just giving us another example of something that could be easily accomplished with the button widget.