I've been using computers as a sysadmin for awhile now. I've had DOS, MacOS 7, MacOSX 10.3, 10.4, MacOSX server, SunOS 4.1.x, Solaris 2.2->10, Gnome, KDE, FVWM, Windows 3.0 -> XP, Cygwin, RedHat, etc as my main desktop.
The point is, I've had many different desktops as my main system. I've found a Unix system with virtual workspaces with a large screen or dual screens works best while I'm at work with > 50 application windows open. I prefer Linux because the tools I need are easily available as part of the distribution. If I'm adminning windows, I've used VMware in a pinch. A remote desktop to a 2nd system running windows is better. When MacOSX is involved, VNC over an SSH link to a Macintosh works well. Gigabit ethernet makes this very feasible.
At home, my main machine is a Linux laptop. I tend not to use more then 1 workspace. I VNC to my MacOSX box and rdp to the family PC running Windows XP. My server runs Solaris 10 for ZFS. I have gigabit at home too. I've gotten so 802.11g feels slow. I think I could be happy enough with Linux, MacOSX or Windows with Cygwin at home.
It really depends on what you're doing. Macintosh OS and Windows have extensive UI testing to match the standard user. When I'm at home, I'm a standard user. At work, I'm not and I can't change the UI on MacOSX or Windows.