Works fine for me also on Mac (ver 2.0.2 build 2221, OS X 10.7.5).
On the Mac, I find drag-and-drop works as a two-step operation: first select, then (with an arrow pointer) dragging the highlight. The position where the text will be dropped is indicated by the blinking cursor.
When you're trying this, after selecting your text, you may need to move your mouse so that the pointer is clearly outside the selection and changes shape, then move it back over the selection. If your mouse pointer isn't changing shape, then you'll have to find out what's causing the atypical behavior, eg., a plug-in conflict or using an earlier version with a bug.