“The timing of [Chrome for Mac] has been one of the disappointments of Chrome project for me.”

– Google co-founder Sergey Brin

It has been a long time coming, but Chrome for Mac and Linux is finally here. Google rolled out beta versions of its new browser for both operating systems this morning–more than a year after the company first announced Chrome for Windows. That’s far later than expected–Chrome for Mac was supposed to debut in the first half of 2009–but the browsers have both met Google’s (GOOG) end-of-2009 deadline.

“73,804 lines of Mac-specific code and 29 developer builds later, we’re excited to finally release Google Chrome for Mac in beta,” Chrome engineers John Grabowski and Mike Pinkerton wrote in a post to the Google Mac blog.

“We took a hefty dose of goodness from the Windows version to build a fast, polished browser for Mac–with features such as the Omnibox (where you can both search and type in addresses), themes from artists, and most importantly, speed. We also took great care to make Google Chrome a native application for Mac. For example, we integrated the Keychain into Google Chrome for Mac, and incorporated Mac-style animations when you open the Bookmarks bar.”

Google Chrome for Linux boasts similar attention to detail and the open-source development process. “Google Chrome works well with both Gnome and KDE, and is updated via the normal system package manager,” Google engineers Dan Kegel and Evan Martin explained in a post to the company’s Chromium blog. “It has also been developed as a true open source project, using public mailing lists, IRC channels, bug tracker, code repository, and continuous build and test farm–following in large part the trail blazed by Mozilla.”

The engineers explain that “Where we noticed problems in system libraries, we pushed fixes upstream and filed bugs. This open approach to development seems to be working: so far, about 50 developers outside Google have contributed code (for instance, thanks to Ibrar and Pawe? for our FTP stack), and several Linux distributions even maintain preliminary open source builds of Google Chromium.”

This latest version of the browser offers a number of new features. Among them: Private browsing, location-aware surfing, support for emerging HTML 5 standards such as plug-in-free video and audio playing, and better JavaScript performance. It’s that last improvement that’s most noteworthy since Mozilla claims that Firefox 3.5 is twice as fast as Firefox 3, and an astonishing 10 times faster than Firefox 2.0.

Nice features, all of them, and ones that certainly reflect the goal of Firefox’s creators at the Mozilla Foundation: To upgrade the Web. “What we’re actually trying to do,” Mozilla Chairman Mitchell Baker said at our D7 conference in May (see video highlights below), “…is improve the Web itself….Our main goal is to make more capabilities available, and right now, the browser is the main delivery mechanism….We’re trying to be the delivery mechanism upon which others build innovations.”

And upon which Firefox builds market share. Though it is currently the world’s second-leading browser, with a 22.5 percent share of the global Web browser market, Firefox faces some formidable competition these days from Microsoft (MSFT), Apple (AAPL) and now Mozilla partner Google (GOOG), which is bearing down upon it with its latest “don’t-be-evil” bulldozer, Chrome.