Ask HN: Best JavaScript drag-and-drop plugin?

We're migrating a Flex app to HTML and are currently considering drag-and-drop.

Considerations: obviously we want it to look great, but it also needs to be easy to tie in Ajax calls to drag events. We'd also like to enable this functionality with multiple UI areas.

Has anyone had good success with a particular plugin? Or is that a hopeless cause and we should just write our own?

We're trying to stick with jQuery for our overall framework.

We'd like to check on any feedback from HN before diving in.