Support!

Source
C|Net reviews of OSX and Vista on 1st November

Lets look at the "Technical Support" prices, I think they are applicable in US.

OSX - 90 days free, then $49 per incident

Vista - 90 days free, then $59 per incident

Ubuntu - $250 + Taxes(no idea how much) per Year, for 9x5 support (9 hours a day, 5 days a week)

24x7 support for Ubuntu costs $900 + Taxes per Year, but I think it's not worth that much.

I'll just say three things, apparently few people in my friends and family love Vista!

1. I have helped someone to find out reason for frequent reboots of a laptop, apparently she thought it was cuz of virus in OS, but it was a hardware problem in the end.
2. I have helped tons of people on how to install Windows(sadly).
3. I got a "few" people to shift to Ubuntu, even though I was using XP back then ;-)
   

OS costs ( from the same review)

OSX - $129 single user license

Vista ( I think OEM prices are lower, but you better check them yourself)

1. $99 Basic
2. $159 Premium
3. $199 Business
4. $259 Ultimate

Ubuntu - $50,000,000,000 for single user license :-D