"So does anyone have a really strong reason NOT to use -s?"

Now, I will ask the other way around, does anyone has a strong reason why -s should be used.

I have this principle in general that, when you code, you don't do wierd things.

"He also says that since he is the only one that uses his scripts and because he does validation "

The world is changing everyday, so tomorrow he might no longer be the only one. He does validation, true, but by using -s, his code is much more fragile, probably becomes another piece of crape that nobody else wants to maintain or touch.