Chris Blizzard of Mozilla gives a great interview to der Standard in which he highlights how Firefox is increasingly pushing the envelope on browser innovation. If you've taken a look at Mozilla Labs lately, you'll understand what he means.
While Mozilla may not have innovated everything in the browser wars (e.g., tabbed browsing, which arguably came from Opera), it is responsible for driving these innovations onto more than 150 million desktops worldwide.
The most salient point for me is that Firefox is gaining market share because it is better, not because it's open source. Firefox, then, is a classic example (as with Linux on the server) where it is rising because of its quality, not because of its cost, code access, etc.
I had breakfast this morning with John Lilly, CEO of Mozilla, and while John isn't prone to self-aggrandizement and was quick to point to the Mozilla community as the source for much of Firefox's success and innovation, he indicated a range of new projects under way at Mozilla that are setting standards for usability and functionality in the browser. You can see a glimpse at the Labs site mentioned above, or simply by typing into the address bar ("the awesome bar").
In a similar manner, Mark Shuttleworth isn't resting on his Linux laurels and expecting people to use it because it's free. He wants to make the Linux desktop better than the Mac desktop. He's setting his standards high. Knowing Mark, he'll likely achieve them.
This is the future of open source: not code that just happens to be free, but code that just so happens to be better.