In many ways this is a very good product, and does make a very nice mug (singular) of tea. I particularly like the fact that when the water is brewing, the dual wall created by the brewing chamber and the jug keeps the water nice and hot.
That said, having bought the 1000ml model, I can see no benefits of this over the smaller, cheaper models. Given that you can only make one mug at a time, I would, in retrospect, go for a smaller model. While you could fill the jug of the 1000ml model by brewing twice, the glass of the jug alone has pretty poor thermal properties, rapidly cooling the first brewed tea while you wait for the second. I dislike luke-warm tea so I never do this, instead pouring the first brewed tea before starting the second mug brewing. As such, the larger 1000ml jug is never filled.
Essentially, the product would be many times better if the size of the brewing chamber was commensurate with the size of the jug. Ideally, a single filling of the brewing chamber would fill the jug. Given that it doesn't, I'd recommend the smaller model.