Please note that the advantage in these cases is only in the number of characters that you need to type.

Reducing typing has always been its purpose and that is what it does well. I hate that you have to use parens here and would in practice probably indeed use length $_ instead of length(). (I find the latter rather unreadable the more I think about it. It looks as if I'm trying to explicitly pass NO arguments.)

I prefer to leave out $_ when it can be implied, because that is what I think improves readability. I even like to abuse for for topicalization.