We have lots of them, they are much smaller than the tables, and that will allow us to do the migrations more incrementally.
One area where the documentation is not very detailed - What are the side effects and/or constraints put in place while an index is being moved? I assume that the index will not be available to the query planner/engine during that time period. Are there other ways in which the table (and other indices) are affected or locked?
Cheers,
jason