C++ Developer - must admit I used to use spaces, then switched to tabs.
This was for several reasons - firstly - makefiles will not be parsed correctly if you start using spaces rather than tabs, so it's a good habit to get into to use them elsewhere to save headaches. Secondly, almost every developer I've met will want to use a different amount of spaces for indentation. When using tabs they can set whatever they want using the text editor or IDE of their choice.
This was for several reasons - firstly - makefiles will not be parsed correctly if you start using spaces rather than tabs, so it's a good habit to get into to use them elsewhere to save headaches. Secondly, almost every developer I've met will want to use a different amount of spaces for indentation. When using tabs they can set whatever they want using the text editor or IDE of their choice.
This is my line of thinking anyway.