Let me preface this by saying that I love Python and it is currently my language of choice for doing almost everything (I prefer C for things that need to be really fast).
I have an anecdote regarding a whitespace issue. I had an infinite loop that was supposed to sleep after it did the work if there was work to do. The sleep was there, but it was off by one indentation so the program was consuming 100% CPU, think:
{some arbitrary code...}
while True:
if condition:
do something
elif condition2:
do something2
else:
do something3
# if conditions aren't met sleep until there is work to do
sleep interval
So the sleep was in the else block causing the program to rip through CPU (fortunately there were 4 on the machine, so it was really only 25%), but the point is that things like this can be hard to see.
This is a perfect example of trade-offs, IMO. You either have to deal with the scoping with extra parenthesis or you have to pay more attention to the indentation.