The empty section to the left of the photo is where you cannot see the Pope because you are too close to the colonnade under the window he appears from. The space in the centre is railed off. You can just about see the beginning of the crowds stretching up the Via Della Conciliazione. So the reports speaking conservatively of "more than 100,000" are certainly right and the "nearly 200,000" figure quoted in other reports would be perfectly reasonable.
This is about ten times the number that normally gather for the Angelus on Sunday. Forza Roma!
At the Vatican website, you can read the Angelus address in Italian. Before the Angelus, the Holy Father gave his customary catechesis (today on the Octave of Prayer for Christian Unity). After the Angelus, he thanked the students and professors who had come, for expressing their solidarity with him, and Cardinal Ruini for promoting the occasion. No time to translate it now but I'm sure it will be round the web in English within a short time. Here is a quote courtesy of AP:
"As a professor — shall we say, emeritus — who has met with so many students in my life, I encourage all of you, dear university students and professors, to always be respectful of other people's opinions and to search for truth and goodness with a free and responsible spirit."Back of the net!
One more photo - thanks to Fr Z:
The banner reads "Christ is the true Wisdom (Sapienza)".