I'm only into part-time/hobby development and so havent been able to justify spending the time (or the money) to do a Unix based OS setup for this, since all my machines run Windows.
With a node executable and native Windows support, it means i can have a dabble more often, which could lead to completion of a real project, even if im only working on it part time. I think for that reason alone, it will increase adoption of Node many fold. Not that i have anything against Apache, but it might just get unseated as the hobbyist's first choice as multi-platform web server (assuming its still on the top spot. I havent used it in ages).
I just hope it doesnt get restricted to the Windows Server family of OSes. I did a quick dig, and can see Windows 7 supports IOCP, so i'm hopeful.
If you do want to see a new cool API that Node.js should eventually take advantage of, check out User-Mode Scheduling in Win7+ at http://msdn.microsoft.com/en-us/library/dd627187(VS.85).aspx ; you can schedule your own async IO threads in userspace and save on kernel transitions.
(I've meanwhile reversed my setup to reflect the majority of my dev work: physically installed Ubuntu, virtualized Windows.)
I do see what you are saying though, and its ideal for someone that isnt as unfamiliar as i
Having a reflective moment a couple of weeks ago, I decided to learn something completely different (for me) and try Ruby. Not wanting to become type-cast as a Windows guy, I chose to do it on a unix based system. For this, I use an Ubuntu image in Virtual Box, and have been very happy.
> I just feel 'safer' in Windows.
I guess I could say I'm the same, though I think its more down to simply preferring Windows 7's UI/UX over the likes of Gnome and KDE. I've also tried customising a whole variety Linux window mangers, but always gave up.
So what I'm doing now is using Virtual Box in headless mode, then ssh-ing in with X-forwarding enabled. This gives me new icons in Windows 7's task bar for every 'remote' Linux window I have open. (though really I don't use much more than a terminal and maybe gvim). To an observer looking over my shoulder, it would just appear that the 'remote' Linux applications are native Windows programs.
 I didn't really address your point about the learning curve to learning a new OS. This is valid issue and all I can suggest is to give it a try, and using a VM is an easy way to just dip in. You can get pre-installed Virtual Box images for many Linux distros such that it is really easy to get started. Unfortunately, my set-up took quite a bit of effort to get started (even with my familiarity with unix), but using a full-screen Linux VM is a good place to get started.
I guess what I was describing is just where you can go with it once you're comfortable.