Is there a gesture to drag and drop with Expose on Lion?
I don't know when this has been re-enabled, but in OS X Lion 10.7.4 I am able to do the following:


Click drag and object in Window A and hold it with your thumb.
Initiate App Exposé/Mission Control using a four finger gesture. Do not release your thumb.
Drag the object to Window B using one of the remaining four fingers. 


So, this is basically the same as you used to do.