Chromium is the open source browser developed by Google. The differences between Chromium and Chrome are very minimal. Chrome has custom icons and other parafernalia that, due to licensing issues, can’t be made available in Chromium. Chrome is also available as a binary for Microsoft Windows operating systems, and can be downloaded from the Google Chrome Web site.
Other than that, Chromium is a fully functional browser product that is currently available only as source code. Chromium is available for Windows, Mac OS X and Linux. The Mac OS X and Linux ports are still under heavy development but are becoming more and more usable over time.
For more than a month I’ve been tracking development of Chromium for Mac OS X. I’ve been building and testing Chromium for Mac OS X myself  and my general impression is that development pace is pretty fast. For example, yesterday, a mock Preferences dialog box was added. A few days ago, working support for draggable and dettachable tabs was also added (previously it was possible to detach a tab from a window but it was not possible to re-attach it to an existing window).
Overall, the Mac OS X port of Chromium is getting more and more usable and stable. I’m now able to use it for most browsing tasks. The look and feel matches perfectly Aqua but also resembles a lot its Windows counterpart. While it is true there are a few annoyances, like losing the focus on edit controls when switching tabs, or tabs crashing at times when executing a paste operation, they are getting fixed in each iteration. The browser feels extremely fast when compared to Firefox 3.0 and faster than Firefox 3.1, Safari or Safari 4 beta. Heavy and complex Web pages like Google Reader or Google Mail load almost instantly while still looking correct. Some Web pages get rendered slightly different from other browsers. As an example, Google Mail looks slightly different with bigger spacing between lines in the mail thread (main) view and also slightly smaller fonts, but these are very subtle differences that do not affect usability or readability.
I must confess I’m pretty impressed about Chromium. When Google disclosed Chrome and the initial availability for the Windows platform only I was very disappointed. I also thought that it’d take much longer to see a nearly-functional port for Mac OS X or Linux. But I was wrong. It is good to be wrong. Let’s hope the development pace keeps on the same levels 🙂
PS: By the way, this post was written entirely from Chromium in Mac OS X. The tab crashed a couple of times but WordPress has a nice auto-save feature that I really appreciate 😉