The shaker does hold all the powder, it does snap close tightly, it does do its job. But it isn't great. As mentioned on the forum, to get all the powder in you need to first put in some of the water, then the powder, then the rest of the water. Not a major issue, but not super convenient either.
I'd be an even happier Jake user if the shaker bottle would be a bit bigger, if it would close a bit easier. Maybe if it'd be a bit prettier. Options? Post them!