This page seems to give a fair summary of the main points: http://www.bowness.demon.co.uk/paul.htm
Without going into a lot of detail, I see some pretty flawed arguments on that page. I don't have time to pick the thing apart line by line, but here are a few examples:
It is a common Christian view that after Jesus's death, the disciples spread out and started teaching the gospel stories to people in the Middle East. This is not something that can be backed up from the Bible.
Um, has the writer of this article ever heard of the Book of Acts? It's a history of the earliest spread of the Gospel to the world, including the Middle East and beyond.
Paul insists that it was he, and not the apostles, who spread the gospel.
Where does Paul claim that he and he alone, not the other apostles, spread the Gospel? This is a distortion of what Paul wrote.
Paul told Peter ,"to his face", that he was wrong.
Another distortion, this time of Galatians 2. Paul rebuked Peter over a matter of personal hypocrisy, not over his preaching of the Gospel. Paul does not condemn the message carried by the other apostles.
Paul and the Jerusalem apostles just did not get along, although they came to an uneasy truce. Paul accused them of insincerity and of putting in "false brethren" to spy on him.
Paul does indeed speak of "false brethern" brought in (Gal. 2:4), but he never accuses the other apostles of being the ones who brought them in. This is straw man argumentation at its finest. In verse 2, Paul even says that he submitted his Gospel to those in Jerusalem to 'make sure that he was not running in vain' - in other words, to be sure that the message he was teaching was in concord with the Gospel as it had been revealed to the church. The fact that the false teachers had originated in Jerusalem doesn't mean that they were sent by the apostles. In fact, the Jerusalem council of Acts 15 put a stop to the false teaching of these individuals.
Paul makes clear in 2 Corinthians 12:12 that being an eyewitness of Jesus's life was not what singled out an apostle.
That's simply a false and misleading statement. The verse states, "The signs of a true apostle were performed among you with utmost patience, with signs and wonders and mighty works."
If I were a policeman and I arrested a criminal, I could say that I had "done the work of a policeman." That says nothing about how I came to be a policeman or what requirements I might have had to meet to do the job.
Likewise, Paul says that he performed "the signs of a true apostle." The signs were what showed other people that he was an apostle, they were not what made him an apostle. In 1 Cor 9:1, Paul defends his apostleship on the basis that he had "seen Jesus our Lord."
Acts 17:2 states clearly that Paul taught 'from the scriptures' and not from the evidence of eyewitnesses. Acts 18:23-28 states that Appollos , after he had been taught what was correct and what was not correct about Jesus, 'showed by the scriptures that the Christ was Jesus', not 'showed by eyewitness testimony that the Christ was Jesus'. Romans 1:1-4 states that the gospel came from the scriptures and never states that the gospel came from eyewitnesses. 1 Corinthians 15:3 states that Jesus was raised on the third day 'in accordance with the scriptures' and not in accordance with eyewitness testimony.
The Scriptures (what we would now call the Old Testament) contained many prophecies of the Messiah. The logical way to argue that Jesus was the Christ would have been to show that his life fulfilled the Messianic prophecies, wouldn't it? If Paul had no knowledge of Jesus' life as this article claims, it would have been impossible for him to argue from the Scriptures that Jesus was the Messiah.
That's just from one short section of the article, but I think it demonstrates the level of argumentation being employed.