Hi benjammin,
I don’t have any personal experience with it but hopefully one of the forum members that does will see your post and share their comments. I would make sure that you are clear that this is a wool topper that is designed to affect the “feel” and surface softness of your mattress not a mattress protector that is designed to protect your mattress and have the least possible effect on the feel of your mattress so it’s unlikely to be water resistant or waterproof if that is an important consideration for you. It has 300 gsm of wool fleece on one side (which is almost 9 oz/sq yd) which would be a little less than 2 lbs of wool in a queen size (so you can make some comparisons with other wool toppers) and synthetic polyester fiber with a cotton cover on the other side. If you are comfortable with both the amount of wool (which isn’t a lot) and the synthetic materials in the topper then it would certainly be worth considering.
Although this isn’t a typical all wool topper (which wouldn’t contain synthetic fibers) … if this is the type of product you are looking for then it would certainly be worth considering. If you aren’t sure whether it will be a good choice for you or how you will like it then the return policy of the store you buy it from (and Costco has a great return policy) would also become a more important part of the “value” of your purchase.
There is more about wool toppers in post #8 here and the other forum posts it links to.
Phoenix