Seems to be pretty good. I haven't used it very much yet but it holds the bottle securely. I have it mounted on my road bike and I haven't had a bottle fall out of it yet. Not super lightweight compared to some of the newer material designs out there, but seems like it is pretty rugged and will withstand a crash better other materials.
It seems to only do an OK job of holding on to the bottle. Material is light weight and seems sturdy, but on a mountain bike it seems a little iffy. I'm sure it would be fine for road biking or commuting though, and it's very cheap.