I just began preaching on spiritual gifts yesterday, in 1Cor. 12-14. Yesterday's message should be available sometime tomorrow at
First Baptist Church, in case you're interested. Anyway, I think one could easily confuse abilities that non-Christians may have with true spiritual gifts. Yet a spiritual gift is a "manifestation of the Spirit" and I think, therefore, can only be had by those who have the Holy Spirit. I think they are definitely different from "natural abilities" or acquired skills, though they may resemble these things sometimes. For example, a person may have a natural speaking ability, and that is not a spiritual gift. That same person may, however, receive the spiritual gift of exhortation or prophecy (which I understand to be proclamation of God's Word) or teaching. I would say that the primary difference is that this person's teaching or preaching will be energized and used by the Holy Spirit.
I think with something like the gift of knowledge, it's not just that there is a general intake of learning but that the Spirit enables a person to understand deep truths of God's Word and to communicate those truths to others. In fact, I believe the only place that this is mentioned as a spiritual gift, it is a "word of knowledge", which implies speaking or otherwise communicating, not just learning.