Roman Catholics recognize that apostolic succession and Holy Orders remains perfectly valid for most of the Eastern and Oriental Orthodox Churches. Furthermore, we recognize, in general, that their seven sacraments (we typically work from an identical list) are completely valid, because they have no material defects in matter, intention, form, subject, etc.

While the Eastern Orthodox insist that only leavened bread is valid Eucharistic matter, Roman Catholics feel that there's nothing wrong with that from their perspective.

The reverse is not always true. The Orthodox sometimes accuse Catholics even of not being properly baptized. They do not always recognize the Roman Catholic priesthood as acceptable. The Coptic Orthodox Church recently entered an agreement to stop re-baptizing Catholics. These are great strides in ecumenism when such difficulties are overcome.