I looked for these because my University uses them for new plantings. I was happy to see them on Amazon for a reasonable price.
I just got these a few days ago (including the Gator Jr which is a flat brown doughnut shape that fits under bushes but also doesn't look so obvious in my front yard under trees). It was easy to set up and fill with water. There are two small valves on the bottom that slowly allow water out - the water empties in 6 to 20 hours and the instructions say one refill a week for most new trees is normal. I might fill twice in August heat and am considering purchasing more given the drought-like weather in our area.

This is truly an excellent product. I have used these for years and they last forever. If the zipper starts to get stiff and difficult to close just spray it with WD40 and you're good to go. With small trees that are not established make sure that the treegator is centered and not leaning on the tree...the weight of all the water in the treegator can tip the tree over. Treegator works best on level ground; if using on a slope don't fill completely. I just ordered 5 more but found them on sale and cheaper (by $4.00) elsewhere even paying for shipping. Just google it.

I recently planted 3 new trees and was searching for an easy way to keep the trees watered. I saw the Tree Gator bags being used by our city and that was my introduction to them. They were easy to set-up, easy to fill with water and seemed to release the water slowly enough so the ground could absorb the water and stay close to the tree roots.

Overall I am very pleased with the Tree Gators. The one improvement I would recommend is to make the water intake hole larger so it would allow the use of spray nozzles.