It works well but there are several small problems. It does not completely empty making it hard to move and there needs to be a ridge or handle to keep it open when filling. I have not yet filled it without getting wet.
In general this is a good concept, and one I like better than the upright green hydrators. However, I was disappointed that the material isn't more durable. Since it is placed on the ground, the ArborRain is vulnerable to puncture by roots, sticks and rocks. Which is exactly what happened the first time I moved mine. If the material were stronger and more durable, this would be a great product.
I think the AR 20 is the perfect size. I was able to water my trees on a schedule and only once a week all summer fit around the trees nicely and it was a lot easier than dragging a hose or a sprinkler sround the yard! The only downfall I saw was that if the ground around the base of the tree was not completely level the bag would not drain fully.
The flat design is a great leap forward. Its low profile makes it barely noticeable, even when full. If ground is not completely flat around the tree, I recommend the upright version.
I bought these to you around our newly planted plum trees. After using them for a while I realized that a soaker hose is just as effective if you have enough hose to reach your connection. These may be better suited to remote plantings when you have access to a trailered water tank since you have to fill them in place. I agree with the other posters that a quick-connect cap or other hands-free filling method would be nice. They work as advertised, but you may not need them.