Over at Ref21 Carl Trueman suggests serveral reasons why Protestants convert to Roman Catholicism:
1. A sense of awe and liturgical tradition in much (not all) Roman Catholic worship that is lacking in evangelical Protestantism.
2. A disillusion with the lack of ecclesiology in much of evangelicalism.
3. A lack of confidence among evangelicals in the traditional Reformation formulations of justification by grace through faith, specifically in terms of imputation.
4. The attraction of Apostolic Succession.
5. A lack of confidence in the clarity or perspecuity of Scripture.
6. A perception that evangelical Protestantism has failed on pro-life and moral issues.
This is an important issue. I have met converts to Rome who left their evangelical churches for one or more of the reasons listed above. Primarily, my experience has been that Protestants leave for Rome (and Eastern Orthodoxy) because of the lack of reverence and historical rootedness within most evangelical churches.