When Mozilla made the transition from the Firefox 2.x series to the current 3.x series, they broke a record by netting over 8 million downloads in the first day it was available. Much of this was due to a very successful PR campaign. Firefox 3.5 was released without all that fanfare, but still managed to hold its own. Enough people were interested in the update to net Mozilla over 5 million downloads in the first 24 hours of availability.
What's more, this time they did it without any server mishaps, no doubt planning for a surge in server load in advance. Whether or not 3.5 is an exciting release is left up to you, but we can all agree that Mozilla has definitely helped changed the face of the Internet in the past several years. Hopefully they will continue to do such as Firefox becomes a more serious competitor than ever against IE.