There are major issues with sidebars containing a lot of widgets (100+)
The first ~30 widgets work correctly, but the widgets further down are not draggable, and sometimes even change the widget order randomly when you attempt to drag them.
Tried all three major browsers (IE, FF, Chrome) without success.
I have made a short screencast showing the issues:
Unfortunately, this sort of instability scares away a lot of users. Hope this can be fixed.