Google's Chrome has generated a browser security defensive arms race and the recent update that address 800 bug fixes and include new security layers demostrates Google is in it to win it. Users and administrators should be overjoyed at the inclusion of built in PDF viewer within a sandbox. Adobe's Reader X also currently will perform much of its tasks within a sandbox as well, however including this layer as a defacto standard in browsers is an excellent move. Google is currently working with Adobe to place to run Flash within the Chrome sandbox and a release is available for Windows at this stage. Sandboxes are not a cure all but just another layer of defense, what is interesting is that browsers now are addressing extension/plugin security with the us of a sandbox.
Ultimately we must continue to demand higher quality of code from extension/plugin developers and not place all our defenses in sandboxing. (Developers must still ensure secure coding principles such as verification, validation and unit testing and not fall into the trap, "Oh the sandbox will take care of that.") Chrome is an excellent browser for the Mac Platform, has a robust set of extensions, and should be considered an alternative to using Firefox especially on Windows systems in dual office deployments. Safari is still hard to beat in Mac OSX but I think that Google really is producing a quality product in Chrome which users should really consider using.