what really drives me nuts is editors that like to write 4 spaces for one indent, tab character for two.

the more general problem with tabs is that someone invariably is going to want to indent a wrapped line an additional 6 spaces and is going to do it with a tab and two spaces, and someone else is going to try to display tabs as 3 spaces and it won't line up.

it may not technically even violate your rules above (tho 5 is ambiguous enough it may apply).

you've also taken away the ability to use the tab key to speed the alignment of tabular arrays.

to say, i agree in principle, but not in practice. the easiest way to get consistency is to restrict freedom -- soft tabs only, 4 spaces per indent.