Remove soap scum with a razor blade

I know, this is gross.

I went a long time without really giving our shower tile a thorough, deep clean. I kept thinking we were going to remodel the bathroom, so why bother? Well, that hasn't happened, so it was time to tackle the scum. But how? It just so happened that my very handy father was visiting a couple of weeks ago, and he said that he uses a razor blade for these kinds of jobs. Really? Wouldn't it scratch? Nope, not if the blade is new. So, since he's awesome like that, he went and razor-bladed our bathroom tile. Now you see it...

...now you don't. And no scratches!

You don't need to use a lot of pressure, just gently scrape it off. Gone. Then you can follow-up with a paste of baking soda and water, using a scrubbing pad (lightly) to work it in, then rinse with water. I've also read that full-strength vinegar will give it a nice, clean shine. This is the magic tool I'm talking about:

From what I've read on the interwebs, you can also use it on glass shower doors.

Have you had success removing soap scum using non-toxic methods?