But my editor can do the indentation for me based on the braces. And if I change the control flow (for example, moving a block of code into an if), the editor can easily reindent the whole block. So using whitespace for indentation doesn't save me any work and in some cases takes more work (when I have to manually adjust indentation because the editor can't figure it out).
It's a relatively minor annoyance, and I'm actually a big fan of Python. But I sometimes wish it had an "end" keyword like Lua or Ruby.