For example, the Mac beta integrates features like OS X's built-in sandbox system, spell-checker, and Keychain -- not to mention that 73,804 lines of Mac-specific code were written. Meanwhile, Google designed the Linux version to have tight integration with native GTK themes, updates that are managed by the standard system package manager, and more.
Google did note one small, and hopefully temporary bummer about the OS X version. While Windows and Linux users have access to more than 300 extensions, they "aren't quite beta-quality on Mac yet." If that's okay with you, download Chrome here: OS X | Linux