I used this protector with the rain 3.0 pillow. It worked great, but I felt like the cooling effect of the pillow was slightly reduced. 
Overall protection was actually really good! If you have kids, or you ever take your pillow out camping, this protector is a must have. Before purchasing, noise while moving at night was of concern. That concern went away the moment I tested this pillow protector. By the way, I've used this protector for about a year now and it still works quite well. I just hope they release a 6.0 version like they did with the mattress protectors. 
Chances are, you own an expensive high end pillow if you're looking at this product. Make it last with this protector. Don't have kids and don't take this pillow camping? Don't even worry about getting this protector. You could probably get by without it.
Also, I wish I could give this product a 4.5 out of 5 stars. But that isn't an option, and I'm not about to give away a perfect score.