[rbanffy]

> 1. Windows was never originally designed to work as a Server side operating system at the first place.

That's not exactly correct. Windows NT was designed to compete against Unix in the desktop workstation and non-dedicated server market. It was designed by a team formed mostly by DEC alumni. I call it "the bastard child of VMS" for a reason.

> 8. Unix is open source, its freely available.

Linux and BSD are, but OSX and Solaris are only partially open source and AIX and HP-UX are very proprietary.

> 10. Lack of multiuser login,

I believe Windows servers can currently host more than one user session. I used this with NT TSE and I don't think this feature was removed since the late 90's (when I used it). It may be some idiotic license restriction.

> 11. GUI overhead

Windows' GUI is rather primitive. I can't imagine the resources it consumes are relevant these days. I have seen more sophisticated stuff on Symbian phones.

[T-hawk]

> I believe Windows servers can currently host more than one user session.

Yes. Windows XP and Server 2003 Standard allow one local login plus two Terminal Server (remote desktop) sessions. Windows Server 2003 Enterprise and Datacenter Editions allow more (but nobody ever bought those flavors because Standard was so much cheaper.) I'm not familiar with Windows 2008 Server but the policies are probably similar.

The limit of two remote sessions in the regular editions is arbitrary, but was chosen mostly for RAM constraints; the windowing environment for each user plus the tasks they're likely to run will consume a few hundred MB of RAM or more. The advanced editions support RAM beyond the 4 GB 32-bit limit.