I'm asking this in the poll as well. If you marked "No, please keep it", please let me know why. Specifically, how do you normally use that feature?
I'm asking because I think I can make it go a lot faster (and thus be able to include many more words at a time) if I get rid of the reordering drag and drop. You would still be able to use the new back button to go to a previous word, and you'd still be able to click on any word in the river to skip to it. If you could still do those things, do you still want to preserve the drag and drop?