Tabs vs Spaces - Code Formatting

Do you format code with tabs or spaces? It is not an a question of what is pretty. There is more to the story. I would like to quote from[1]

"On defaultly-configured Unix systems, and on ancient dumb terminals and teletypes, the tradition has been for the TAB character to mean move to the right until the current column is a multiple of 8. This is also the default in the two most popular Unix editors, Emacs and vi.

In many Windows and Mac editors, the default interpretation is the same, except that multiples of 4 are used instead of multiples of 8."

The code formatted on Windows using tabs look hideous on Unix, while if you use spaces it will be uniform on all operating systems.

[1] http://www.codinghorror.com/blog/archives/001254.html