Which is precisely why tabs-only is a problem: tabs cannot express character-granularity alignment, so you HAVE to mix them with spaces in this way. (Or give up pretty alignment in favor of fixed indentation for continued expressions, which I'm not willing.)

Spaces just get out of my way.

P.S. I'm undoubtly biased by Python. The community's agreement on spaces and specifically 4 spaces has been a pure blessing.