The 18 Tir uprising involved only students who were asking for greater freedoms of speech and the press. However, the current uprising in Iran is not made up only of students but of people from all parts of society. That has partly to do with how many people participated in this election. They all feel as though the government owes them something.
Perhaps the biggest difference between 1999 and 2009 is that the people are wiser and far more experienced at dealing with the regime. In 1999, we were hot and angry and unfocused. The protesters of today are much more calm and purposeful, more experienced. They know how to deal with the government, how to embarrass it through nonviolence and civil disobedience.