I would characterize the content as "conservative Christian." It contributors are a mixture of orthodox Catholic, conservative Protestant, and Orthodox Christian writers, striving for some sort of ecumenism. Touchstone is an admirable effort, but C. S. Lewis' concept of "Mere Christianity" is necessarily merely Protestant. See the article by S. M. Hutchens in the New Oxford Review of January 2002. If they intend to be faithful to Lewis' ideas, then they must limit their discussion, though certainly not their participants, to that subset of authentic Christianity "on which we can all agree," or some such construction.
I think this is an idea best honored in the breach. My impression from a few readings is that Touchstone is already finding it necessary to venture outside the confines of "Mere Christianity," and that they will find that true ecumenism must lead them to something a good deal less "mere" and a great deal more authentic. I welcome that inevitability.
Agreed then. Also, there is a helpful distinction to be had between orthodoxy and ecumenicism.