Yep, I have a couple of them and I drag them all over the place when I'm traveling.

As long as you're pulling on it away from the wall, you'll have the devil of a time trying to budge it.

If you're pulling down or sideways, along the wall, it can budge but it takes some doing.

Put as much pressure on the suction cups as you can muster before setting the clamp.

I had them in my dad's shower too and had the cleaning lady remove them every time, clean and dry the wall AND clean and dry the suction cups before replacing them. He was very satisfied with them for the 3 years he used them.

Honestly, Jane, the price is fair and it couldn't hurt to really put one to the test under controlled conditions. If you're not satisfied, there's your answer.

If you have textured tile, or any porous surface, they will be less reliable and I'd recommend against it.