What does a short narrative such as the apostolic visit to Iconium add to the overall thrust of Acts? It is easy to see why the sending of Paul and Barnabas is recorded. Similarly the foundational conflict between the good news and evil in Paphos and the evangelistic sermon in Pisidian Antioch. But the visits to Iconium, Lystra and Derbe much less so. It would be simple to conclude that Luke is just writing a travelogue. The places are included just because they were visited.

My assumption is that there are no wasted words in the scriptures and that therefore Luke tells us about Iconium because it is important for Theophilus and us to know about it. One reason might be that Theophilus certainly knows that Christians provoked extreme opposition and divided reaction. The incidents in Iconium show how this started to intensify and why.

I think the chief lesson from the narrative is that what was being opposed, and was also being confirmed by God with miraculous signs and wonders, was the message of his grace. I take it that "the message of grace" in 14:3 and "the good news" in 14:7 are synonymous. The good news = the message of grace.

Why is this important? And why does the message of grace provoke extreme reaction. Recall from chapter 13 that the content of the apostolic message seems to have been:

What God previously promised in the Old Testament he has fulfilled through the resurrection of Jesus (13:33)
Therefore through Jesus the forgiveness of sins is proclaimed (13:38)
Everyone who believes in him is justified from everything that could not be justified by the Law of Moses (13:39)

So the good news is not just that Jesus forgives sins (although it is that). It is that salvation is by grace, not by the Law of Moses, through God's sovereign action and not by our obedience. The message that was being proclaimed and that divided people sharply was that Law-obedience was useless for salvation. There was nothing they could do to earn God's acceptance. It has to be by grace. Notice too that it is the message of grace that God confirmed with signs. Luke is very specific. He doesn't say "the message of Jesus", he says the message of grace.

Granted those things are very close to each other indeed but there is a very helpful distinction for witnesses today to consider. All things considered, non-Christians don't find it completely offensive to hear about Jesus' character, love, parables, healings and the like. But when we start to talk about grace, then they do. When we say that their acceptance by God is only through Jesus and is completely unachievable by themselves, that is the almost the most offensive thing it is possible to say. I recall I college friend of mine who showed she had got the gospel when she went up like a rocket: "this grace is unfair on God and offensive to me. How dare you say that my being sincere isn't enough. If it isn't enough I will do good works." She might have stepped straight off the streets of Iconium.

To conclude:

I expect the message of grace to be offensive to a worldly mind that refuses to bow to God. Accepting forgiveness is deeply humbling. And brilliant.
If people seem apathetic to the message we probably haven't taught the message of grace
Sadly it isn't always non-Christians who find the message of God's grace hard to receive. I know plenty of Christians who still think that they find acceptability from God in their good works or their self-driven avoidance of obvious sins
The Lord confirmed the message of grace with wonders and signs. I think that was a normal pattern. Where I see people claiming evididence of miracles that is completely disconnected from the biblical preaching of grace I am extremely sceptical. But I think we should also ponder if the reason we see few miracle and signs is because we don't teach the message of grace like Paul and Barnabas did in Iconium.
Incidentally note that this was teaching the message of grace to non-believers. John Stevens from City Church Birmingham recently said a very helpful thing to me: the phrase "preach the word" in 2 Tim 4 is often taken to mean "teach the Bible, to Christians", when in fact it meant "preach the gospel, to non-Christians." If I am right that Acts ought to generally be seen as normative as well as formative, perhaps the reason we don't see many miracles is that we have domesticated the teaching of grace and do it more for an internal audience of believers than an external audience of non-believers. That seems to be where the signs were being given