|XP is just a number
I have to disagree on a couple of those.
First of all the diamond operator does not just save 5 keystrokes. Instead it allows you to build filter programs that have a standard (and well-defined) behaviour without your having to build logic to open, test the open, read, close, test the close, get the next filename, etc. When you need it, it is very nice to have. Of course people who use it to avoid writing STDIN are being silly.
But I use the diamond, and not for obfuscation.
As for m operator, I use it as well. Why? Well if I want to match a pattern with forward slashes in it, it is often very nice to use m and a different delimiter. So I don't use it often, but unless I am nobody...