We've had a few of these and they work really well, even over the memory foam topper. The only thing I didn't enjoy about them is that wash water doesn't come all the way out in the spin. Just meant that I needed to spin it out another couple of times.
The protector fit our Queen size double pillow top bed fine even with the 4" memory foam topper on top. I washed it once and put it on the bed. It's just on a guest bed so hasn't actually been slept on yet. It is a little bit crinkly sounding compared with another one we have for our king sized bed. For the price though, it works just fine for our needs.