Didn't it also take that long to port the OS X version as well? (I seem to remember the 'developer' builds of Chrome for Linux and Chrome for Mac coming out at the same time)

Keep in mind that he seems to be mostly using Python and doing mostly number crunching (which would seem to be rather OS independent) from what I could glean.

Isn't the whole point of Chrome to take advantage of OS level protection mechanisms so that stuff coming from the web doesn't get the chance to mess with your machine. I believe they're doing completely different things in this regard on each OS, basically building sandboxes from scratch.