It is probably the most controversial feature. Most people either hate it or love it. I think it's hated mostly by those who don't use Python, and well-loved by those who do.

It was not the first programming language to use significant whitespace, but it is probably the most mainstream one that does, and it did pave the way for other languages to do the same. So it makes sense (IMHO) that sometimes other languages copy this feature, because it makes code shorter and more readable.

I haven't really heard any good arguments against significant whitespace, just the usual "but when I copy & paste a block the indentation might be off" (so use the indent/dedent function in your editor) and "I cannot mix tabs and spaces" (which you shouldn't do to begin with). The "hate" is mostly because people are not used to it. Not unlike Lisp's parentheses...