Cool! I was quite unaware of the difference between || and or. If it makes that much of a difference, I'll start using or in place of || when checking return errors. Thanks for the reply, the information was very useful.
Nononono. Not everywhere. Everywhere it belongs. Neither one is "the right one". Please take the time to understand exactly why they each work the way they do.
Here's a hint: everything you can do with the one, you can also do with the other, as long as parens regulate precedence.