I decided to do the tour so I went up to the meeting point in San Babila, waited there for 15 minutes but no one showed up.
Since it was a holiday in Milan, I thought I'd give it another try, so I returned 3 days later and there I met Paolo, the tour guide. It was nice of him of doing the tour even though I was the only attendee. It was a good first glimpse at the city, I learned some new interesting facts. He was a little too stuck to the script, but yet answered politely every one of my questions.
I expected a bit more, having experienced other free tours in other cities in Europe, but it was OK.
In the end, it's a free tour..