Over the weekend I had a few spare minutes and decided to count the number of changes between the RSV-CE and the RSV-2CE. Using the Emmaus Road Publishing Catholic Bible Concordance: Revised Standard Version: Catholic Edition, I came up with well over 2500 changes between the original and the updated. In all actuality, it may be closer to 2800, but I can't confirm that I always hit the right button on the computer when adding it all up. :) Safe to say, however, the number of changes are significant.
Keep in mind, this does not include the changes made to the archaic language in the original RSV-CE, like the "thees" and "thous". So, overall, that is a pretty hefty number in my book. Certainly worth giving the RSV-2CE a second look.
I wonder how this would compare to the ESV?
Update: A few years back a guy, mmortal03, on the Catholic Answers forums tabulated some of the changes in the new RSV-2CE. This was well before the Emmaus Road Catholic Bible Concordance was released and which documented all of the changes. However, his list remains helpful, in particular when comparing the RSV-2CE to the the original 1966 edition of the RSV-CE and the subsequent updates done by Oxford University Press. So check it out!