As a Catholic myself, this really disappoints me:
Now, Catholics around the world will have a tougher time of tracing their roots, as if it isn't already challenging enough in places like Ireland.
Kimberly Powell does an excellent job of summarizing the situation:
Vatican Orders Catholic Parish Registers Off-Limits to LDS Church
The part that got my attention is that the Vatican declared back in 2001 that baptism conferred by the Church of Jesus Christ of Latter-day Saints is not valid. This is the disconnect for me. I have no objection to what the LDS Church does because, given that I don't hold the same beliefs, I don't perceive my own ancestors as being baptized into the Mormon faith. Moreover, if you watch this interview I taped just a few weeks ago with Ahmad Corbitt, Public Affairs Director (NYC) of The Church of Jesus Christ of Latter-day Saints, you'll see that he explains that members of the LDS Church believe that those who lived before us have a choice about the baptism as well.
I personally will gratefully accept and use any Catholic records the LDS Church chooses to make available. And I sincerely hope that some additional thought will be given to this issue and a reversal will be made. Otherwise, all Catholics better start leaving an excellent trail for their descendants!