Before getting to specific issues regarding the translations themselves, I think it would be helpful to examine the origins of the specifically Catholic editions of the RSV/NRSV.
The Revised Standard Version was a revision of the American Standard Version of 1901. The Old Testament was published in 1952, followed by the New Testament in 1946. (A revised NT would appear in 1971.) Seeing the merits of this translation, while also being spurred on by the encyclical Divino Afflante Spiritu of Pope Pius XII in 1943, the Catholic Biblical Association of Great Britain gained approval from the RSV Translation Committee to produce a specifically Catholic edition of the RSV. Many of those who were involved in this process recognized that this was an important step in the improving ecumenical relations of that time. The two principal editors of the Catholic edition were Dom Bernard Orchard, OSB and Reverend R.C. Fuller. Orchard was the main editor of A Catholic Commentary on Sacred Scripture published in 1951. Although this one-volume commentary is now out of print, it was in many places the standard until the New Jerome Biblical Commentary. I happen to own a copy and have found it to be quite helpful even today.
Orchard and Fuller took great care in the editing of the RSV. In the introduction to the RSV-CE, they note: "In the present edition the aim has not been to improve the translation as such. No doubt there are many places where a different rendering might have been chosen on critical grounds. This has been avoided. But there are other places where, the critical evidence being evenly balanced, considerations of Catholic tradition have favored a particular rendering or the inclusion of a passage omitted by the RSV translators." In the Old Testament nothing was changed, except for the inclusion of the Deuterocanonical books and additions to Esther and Daniel. Not even the controversial passage in Isaiah 7:14 was altered, although this has been done recently in the RSV-2CE. The main changes came in the New Testament. For a list of all the changes, see the RSV-CE site on wikipedia. The most notable change comes in the story of the Annunciation in Luke 1:27, where the editors adopted the traditional Catholic translation of "Full of Grace" instead of "O Favored One". Also, whenever "brothers" is used in the RSV, the editors translated it as "brethren". There are also some minor changes and additions as well. In the end, the RSV-CE became the scholarly translation for English speaking Catholics. To this day, it remains the most literal version available and is still very popular in seminaries as well as with many converts to Catholicism. It, along with the NRSV, was the basis for Biblical translations in the English edition of the Catechism of the Catholic Church. The RSV-CE received an Imprimatur from Bishop Gordon Joseph of St. Andrews and Edinburgh in 1966.
The New Revised Standard Version was published in 1989 by the National Council of Churches of Christ in the USA. A Catholic edition was later published in 1991, with Imprimaturs from Bishop Pilarczyk, president of USCCB at the time, and the Canadian Conference of Catholic Bishops. While the original RSV-CE had particular changes made to it, the NRSV-CE contained no changes from the original translation. Part of this must be due to the greater inclusion of Catholic biblical scholars on the RSV Translation Committee. The preface to the NRSV-CE was written by Alexander A. Di Lellam OFM, a Biblical studies professor at Catholic University of America and member of the RSV Translation Committee. Most of his preface highlights the ecumenical dimension of the RSV Committee and the various textual decisions that were made in light of newly discovered manuscripts. In particular, decisions were made in regards to which edition, Greek or Hebrew, of books like Sirach and Tobit were used. Recently, mostly due to HarperCollins, the NRSV has gained more popularity in Catholic circles. It can be seen more and more as the base translation for various Catholic scholarly works. Interestingly enough, most of the NRSV-CE's that have been published recently here in the USA have been the Anglicized text.
If you are interested in seeing the various changes between the RSV, RSV-CE, and the RSV-2CE, this site has it all listed.