I first heard of this technique a long time ago--it made sense then and it makes sense now. But for it to be actually usable it would need some good editor support (I'm not about to micro-manage my editor and alternate between spaces and tabs manually). I would love to see some Emacs code that integrates with c-mode and perl mode. Short of that I have to say banning tabs completely from your source is the only way to make it look consistent across editors.