I know that this is an old topic, but I couldn't help but reply to it.
You claim that transparency, security, flexibility, and cost are main issues. This is false.
I believe the only reason to not make a windows version of the client, would be because you are trying to promote the use of Linux operating systems. I use both Windows and Linux, and can easily tell that both have their own perks.
Windows can be just as secure as linux. Also, Linux is not the main operating system in the market, which is why it isn't targetted as much by viruses or hackers. Windows, since it is the main operating system (still), it will be targetted a lot more frequently. You'd be surprised over how many "powerusers" (as you put it) use windows, and cannot switch to this server software because they refuse to having to completely switch operating systems and set it up. That would take twice as long, without much to suggest that it would be for the best.
There is no such thing as complete security though, even Linux isn't completely safe. Again, I add that if someone knows what they're doing Windows can be just as safe. Of course, it may not be, but it would be close enough that the argument is moot.
As for cost, yes it is pretty high up there if one uses windows. However, a "poweruser" as you put it, probably has a business or is affiliated with a big one. So, the chances are very high that the person has a lot of money. Therefore, this argument is also moot; unless we're no longer talking about power users?