One thing that no-one's mentioned so far is that it makes a fantastic cup of tea! With normal kettles you'd often be boiling water that's been boiled before, which really affects the taste, especially after two or three times. With the Eco-Kettle you're effectively using fresh water each time. It's really rather brilliant.
Of course, there's nothing particularly revolutionary about the Eco-Kettle, except that it can boil as little as one cup rather than the usual minimum of 0.5L. The separate chambers simply mean you don't have to fill it up every time you want a cup of tea - it's essentially a device for lazy people. As another reviewer mentions, you can measure how much you boil (to an extent) with a normal kettle. There you measure at the tap, here you measure when boiling. However, this is perfect for a student living in a shared house who wants to make a cup of tea in his bedroom, or indeed anyone who doesn't have their kettle near a tap.
As for the manufacturer's "cup size" being only 200ml, what difference does that make? It's just a guideline. It isn't difficult to work out that if you need a little more than 200ml you fill the boiling chamber a little above the 1 cup mark.
Overall, excellent product.