Don't forget that the pipe is on the same key on standard QWERTY.
Moreover, there's this retarded use of backslash as path delimiter on MS Windows.
edit: escape sequences
Yeah, sure but it's still two keys to push for the pipe (shift+\ in a US layout, compared to AltGr+< in some European ISO layouts). The escape sequences is the only thing that I use the backslash for, and when you do them, you need to think, so I have no problem doing that. Well, the backslash key debate is actually more about the language layout than about ISO/ANSI, but most of the extra characters on the US keyboard layout is more directed towards technical use, than to regular writing.
In the ANSI layout, the backslash key would be the most "annoying" part for writing anything other than TeX, or programming as it gets in the way of the return key. For me, I can press the ISO return key with my pinky without moving the hand too much, and without bending the finger in any direction. Using the ANSI layout, I need to bend my finger in a crazy way, to avoid hitting backslash, or move my full hand to push return.
I consider the absolutely worst keyboard layout to be the European ANSI keyboard layout, where the backspace key is the same size as any other key on the keyboard, to get the space for the extra key. Here, it's not only that you easily can write the wrong characters, but when you want to remove them, you also miss the backspace key.