The looms I have (a set of four like those in one of the pictures in your link) are very simple to use, and indeed to put down at short notice. If you are in the middle of winding the yarn on, you need to hook the last stitch over before putting down, or the whole row unwinds, but otherwise, it's ideal for work where you might have to stop mid row. Also, if the fabric doesn't work out, it's quick and easy to undo and try again with an alternative pattern. I've been finishing items in a day, usually. It's a good way of using up odd balls.