Google showed an interesting chart yesterday at the first Google I/O keynote. The number of Google Chrome users more than doubled in less than a year from 30 million users in July 2009 to 70 million users today. It's worth pointing out that this is the number of active users, not the number of Google Chrome downloads.
Asa Dotzler has a similar graph for Firefox, which shows that Firefox grew from 265 million users to 365 million users in the same period. To put things in perspective, Firefox has 5 times more users than Google Chrome.
It's a great achievement for Google and Chrome's market share will increase as the stable versions for Linux and Mac are released and Chrome OS becomes available. Even if you won't use Google Chrome, your browsers will be better because more people care about browser speed, process isolation and simple user interfaces.