The decision to use native user interface toolkits on each platform has made it all the more difficult to deliver the Mac and Linux versions of Chrome. Several people wondered why Google didn't just use Qt from the get-go, which would've made the whole process a whole lot easier. Goodger explains that Google "[avoids] cross platform UI toolkits because while they may offer what superficially appears to be a quick path to native looking UI on a variety of target platforms, once you go a bit deeper it turns out to be a bit more problematic." Your applications end up "speaking with a foreign accent", he adds. In addition, Goodger claims that using something like Qt "limits what you can do to a lowest common denominator subset of what's supported by that framework on each platform."
As for the Linux version, Google initially thought that a Windows clone would be acceptable, since Chrome itself is already such a fast application. However, the people working on the Linux version of Chrome made a case for using Gtk+ instead, and Google went with that option. Since Chrome is open source, it could still be possible that a Qt version will be developed independently of Google, of course.
When it comes to the Mac version, Goodger explains that the plan there has been to develop a native version all along. "A Windows-clone would most definitely not be acceptable on MacOS X," Goodger says, "where the APIs for UI development are highly evolved and have many outstanding features. So that's always been the plan there."
The Mac version is coming along nicely, and Google hopes to deliver both the Linux and Mac versions somewhere in June.
Hopefully, they will also implement something like Firefox's NoScript extension because according to some users, the security model is still lacking.