People chill out. I never said bash is better then PowerShell (it's probably not) or tcsh (it probably is ;)) or anything. Same for html/css vs xaml. My point is that you sould learn posix and open standards and platforms first. (xaml is/will get more open as time go by, but I donr see myself recommending learning it over HTML/CSS)
ANother semi-related point I want to make is if you are developing server software for Win32 then stop and think. Why are you doing it. Are you like mysql, trying to expand its user base and platforms? Then great, continue. Are you doing it because you know and are comfortable with windows?
In any case you should learn unix-like systems. Yes it takes effort, maybe much more then Windows, but you have no choice. BTW not talking client - the year of linux on the desktop isn't this one, but we can hear the train coming.