How long ago was that if you don't mind asking? RH used to be preferred. Nowadays I can install from scratch but... I prefer to just roll out Debian or a flavor thereof (apt get is awesome). Ubuntu is about rock solid. I remember the days when Linux was moreso unstable and questionable in use. But Ubuntu is rock solid. There are free virtual machines that allow you to run MS Windows and your favorite Windows apps. Or you can use the WINE (a Windows Emulator). Thusly you can have your cake and eat it too. Ubuntu + Windows running underneath in a VM.
Re: MacOS. Its funny how many people are just figuring out that MacOS is just BSD with Apple-flavored lipstick on.
For those who are sick of MS, its possible to install MacOS on a PC. Or still, one can run MacOSX in a VM under Windows (I have!) or under Linux.
Agreed: Ubuntu + Virtualbox or VM Ware + MacOS or Windows 7 VM-images = win. Dual core or better with lots of RAM is probably the way to go.