In his new book, God Incarnate: Explorations in Christology (T&T Clark, 2009), Oliver Crisp has a fascinating note regarding the appropriateness of using the phrase "Reformed Catholics." He rightly points out that the Reformed tradition was an historic attempt to reform catholic Christianity. Hence, he is wary of talking of Catholics and Protestants. Rather, he wants to distinguish Reformed Catholics from Roman Catholics (p.3, n.8). I have long believed that it is quite appropriate to confess that one belongs to the one holy catholic apostolic church if one has truly believed on the Lord Jesus alone for salvation. For there is one church. It is holy by virtue of the indwelling of the Holy Spirit. It is apostolic, being based on the Apostles' teaching. And it is catholic, in that it is universal.
In this light, there is much to be said for using the nomenclature "Reformed Catholic." Of course, as with all name tags, the term "Catholic" has associations with Roman Catholicism that are not easily shed and that, as a consequence, can easily confuse. When explained it is a great term.
And within that great body of Reformed Catholicity, I am not ashamed to call myself a Baptist.