Who else is using electro-thermal wing anti-/de-icing apart from the 787?
I fail to see what is exactly new in the B787 de-icing system, except for the way it is manufactured (spraying metallic layers onto the composite structure).

Electric heating is the most obvious and straightforward method of de-icing, and the least energetically efficient at that. It is much more efficient to break the ice rather than to melt it - in terms of the energy required. Even B787 with its sheer electric supply can't afford anti-icing (that is, constant heating to prevent ice formation), and de-icing power consumption is 45-75 kW.

Perhaps most Russian (larger) aircraft had electrical wing de-icing system: from Tu-95 (1952) to Il-18 (1957) to Tu-154 (1968) (I could give specific links but they are in Russian). Typically, they work in sections to reduce power demand, and consist of heating wires (rather than layers like on 787) that melt the ice.

Later aircraft such as Il-86 (1976) and -96 had a more advanced electric impulse system, which creates mechanical impulse on the leading edge with induction coils. This deforms the skin for a very brief moment to break the accumulated ice.