I've been programming in Python for 4 years and I've never spent hours trying to find an indentation error.

It comes up, sure, but no more frequently than any other syntax error in a different language and there are usually dead giveaways indicating what happened. Most IDEs/editors have options to view whitespace characters, so if you're worried about encountering a bug from this you can always enable that feature.

It's really a non-issue.

Well I've written quite a bit of CoffeeScript, and while I had a few issues with incorrect code translation to JavaScript, I don't recall ever having problems with mis-indented code.

As another point to triangulate from, Haskell is also whitespace-sensitive and I have never had a non-trivial whitespace error in it.

This one won't.