In the midst of the controversy and contentiousness surrounding Paul's (and his associates, including by name here, Apollos) ministry, he makes several key points here which are worth applying to the Church generally today and (with care and respect) to ourselves.
1. Those with a ministry are carrying out a sacred trust; it is a gift of God, and ultimately only God is worthy and capable of assessing the value of the gift in each person. God's ultimate judgment will expose the true hearts and motives of all persons.
2. Without denying the need for each of us to search and know our own hearts, Paul states that ultimately any human assessment of the heart and human-based truth does not carry weight; such assessment can fail.
3. Paul specifically appeals to Scripture in insisting that truth is "nothing beyond what is written" (in his time and context, that would comprise the Old Testament canon only). No human teacher is above another.
"If anything has been given to you, why boast of it as if it were something you had achieved yourself?" (v. 7, J.B. Phillips trans.)
Here is a warning to all of us: even if the boasting is purely within ourselves (and it so often is something I catch in myself), consciously or unconsciously, we are making a value judgment: that we are intrinsically better than others. And that is dangerous thinking, for we are setting ourselves up to be exposed.
I'll be better advised to boast of the giver of gifts, and thank the Giver truly from my heart.