Minor changes to the wording of many portions of the Mass will be obvious to Catholics. The repeated exchanges "The Lord be with you" / "And also with you" between a priest and his congregation, for example, become "The Lord be with you" / "And with your spirit" in the updated version.
The prayer said before Communion would become "Lord, I am not worthy that you should enter under my roof," instead of "Lord, I am not worthy to receive you."
Personally, while the American translation wont directly affect Mass in Ireland, I think its a little silly to change the prayers that people have been using all their lives. Especially when the version you are changing to makes slightly less sense and is somehow less personal than the original. To me "enter under my roof" sounds less personal than "receive you" when taken in context of being about to receive Holy Communion.
I'm not against change, and I personally don't go to Mass much, but I think it's a little daft to fiddle with words like this when the Church has far more pressing issues to deal with if it hopes to rebuild its reputation and congregation in it's 3rd millennium.