Mark Shea writes that he “never met a living soul who really believes in salvation by faith alone.” He needs to get out more. He also describes doctrinal differences (between Catholics and Protestants) as "gigantically inconsequential".
This is quite wrong. Even a cursory investigation, by Protestant or Catholic, into the two views on salvation, with particular attention paid to the role of the sacraments to the Catholic, will reveal the differences to be far from “inconsequential”. The Catholic Church understands this enough to have condemned to eternal damnation those that profess Sola Fide. And Protestants (and not just of the Reformed ”species” as Mr. Shea suggests) understand now, just as in the 16th century, that the differences are so substantive that a schism was inevitable. So, Mr. Shea, if you meant what you wrote: “[You] don't worry about the ‘faith alone’ sloganeering so long as they don't take it seriously”, well, it’s high time you started worrying. We take it very seriously.
This is not to say that Protestants and Catholics cannot "get along" or have cordial discussions. But it makes little sense to characterize significant doctrinal differences as "inconsequential".
[UPDATE: Also responding to Mark Shea's post, Mark Byron has a good post on the Trinity.]