I just came across a blog post with an example on how to create a drag & drop effect using jQuery UI.

Looking at the code it surprises how easy it is. The whole JavaScript is around 17 lines of code, but but only around 9-10 of them are directly related to the drag functionality.

But after hearing Paul talk about all the casuistics he was considering when implementing this functionality I would say that the most important characteristic is not simplicity but robustness.

Ever build a drag & drop effect but fails when the user moves the mouse out of the browser window? what happens if the mouse button is released in another app? etc, etc. That's the real hard part of drag & drop and is great to see Paul and the jQuery UI guys pay so much attention to these details.