I agree with Xyon. An operating system is just the most basic component of something the user customises to allow them to do what they want. The very strength in an OS is the ability for it to run a myriad of tools.
I'm more than willing to bet that any person who says 'I hate [name of OS]' is complaining more about a particular tool in that OS rather than the actual OS and these days, with tools like hypervisors becoming more mainstream the OS itself is becoming nothing more than an additional tool.
At work, I have a Windows XP laptop. On that laptop I have Orcales virtual box. Inside Virtual box I have Windows server 2003, Windows Vista and CentOS 5.4
Each one has a specific role, the XP machine is my main machine. The 2003 server is testing out some custom GPO templates, The Vista box is testing out a GPO settings and the CentOS box allows me to do file administration on storage arrays we own.
I couldn't do it from a single OS because each OS has a specific reason for needing to be used. Windows XP can't run active directory and I need to keep AD segregated from the main network, this is not a limitation of XP but a fact of both the operating system and what it is meant to do and network security.
The Windows Vista box is required to test out a Vista specific GPO, I can't deploy to XP because A. the XP box has all the email and day to day stuff I use, if I break it I'll have problems so it makes sense to use a VM and B. The GPO is specificially for Vista.
The CentOS box is required for NetApp filer administration. I can do SOME of this via SSH but with a CentOS box I've got better file manipulation controls and can use SSH keys so I don't have to muck about with passwords.
So, Each OS has it's own specific reason for being used. There are no favourites. They all work with me to help me do my job.