I attended the Winter Olympics in Torino in 2006. But, I guess you're asking about summer events. I will say that the unexpected cool thing about those Olympics is that for every "A" event ticket we bought, we also had to get a "B" event. A couple of those "B" events were a lot of fun - especially Curling. We did buy some "A" event tickets online, which did get you around the two ticket requirement.
We did have a great time. There were some great athletes and the interaction with fans from all over the world was a trip.