Here is Simon Chan's concluding paragraph in the upcoming Four Views on Christian Spirituality (the 4 views are Roman Catholicism, Eastern Orthodoxy, Evangelicalism, and Liberal Protestantism):
[This book] beyond helping us appreciate the similarities and differences, the strengths and weaknesses, the exchanges between the interlocutors also highlight at least three other important implications. First, they show that our common Trinitarian confession has spiritual ramifications too large to be adequately captured by any one spiritual tradition. If that is the case, then, second, the mutual critique and appreciation should lead to self-correction and transformation from within. Third, the awareness of each other's strengths and weaknesses should serve to motivate all toward a more holistic and ecumenical spirituality. Hopefully, evangelicals will come away with a better grasp of Catholic comprehensiveness, Catholics and Orthodox Christians with a fresh injection of evangelical fervor, and mainline Protestants with both.
(Simon Chan, 'Foreword,' in Four Views on Christian Spirituality, ed. Bruce A. Demarest [USA: Zondervan, 2012], pp.8-9)
The last sentence is an astute critique on the spiritual bankruptcy of the 'Liberal Protestantism'. Chan is here saying that Evangelicalism, Roman Catholicism and Eastern Orthodoxy have substantial contribution to offer to all traditions to learn, while the "mainline [Liberal] Protestants" not only has nothing to offer for any of the other three, it has nothing even for itself.
Kian-Seng has written a review of the book.