Re: If you've got to do all this work to change your OS..
Lets work through your reasoning
"Because so many applications runs on windows only"
Chances are there's a more-than-viable alternative on Linux. Even if you think Libre-Office doesn't cut the mustard, Kingsoft Office will more than easily fit the bill to replace Microsoft Office, for example. Else, run WINE
"because so many users are used to Windows UI"
Which is being deprecated by Microsoft in favour of Metro. At least most Linux distro's keep some sort of familiarity
"because finding and installing drivers on Linux can be such a pain in the arse"
And almost always not necessary. Even if your driver isn't built right in, the Hardware Driver tool in Ubuntu will do it all for you
"because WS servers, Active Directory, centralized authentication, GPO are so useful and easy"
WS Servers: I assume you mean windows server. And no its not any easier to set up, its just different.
Active Directory: Supported in Linux. Look up Samba
centralized authentication: Supported in Linux. Look up Kerberos
GPO: that ill give you, but there's still NIS