I used to be a linux server guy, RedHat (I feel so old saying that) - but then Windows Server 2003 came along, IMO the best server OS ever made. Stable, with the updates it's practically perfect for everything I need.
LukaszR- what do you think of 2008? Every time I see the OS, all I can think of is "Windows Vista Server Edition" and then I crawl into a hole and hide