Tim Challies writes on http://www.challies.com/ and wrote an interesting blog on Why he is not a Roman Catholic. I appreciated the Scriptural content that is found in the links within his article and the balance of these two paragraphs:

I joyfully affirm, of course, that there are true believers within Catholicism and that what is true of Rome’s official doctrine is not necessarily true of all of her adherents. Yet the salvation of these brothers and sisters has come despite the teachings of the church, not through them. I appreciate the point Leonardo De Chirico highlights here:

What refers to the Catholic Church in its doctrinal and institutional configuration cannot necessarily be extended to all Catholics as individuals. The grace of God is at work in men and women who, though considering themselves Catholics, entrust themselves exclusively to the Lord, cultivate a personal relationship with Him, read the Bible and live as Christians. These people, however, must be encouraged to reflect on whether their faith is compatible or not with belonging to the Catholic Church. Moreover, they must be helped to critically think over what remains of their Catholic background in the light of Biblical teaching.

You can read the entire article here: http://www.challies.com/articles/why-i-am-not-roman-catholic