I tend to use triads a lot more, even as a standard power chord that extra note fills in the sound more, and playing Opeth you almost have to in order to get the dissonance. You can switch around power chords a lot though, and they can be very effective when a lot of other things are going like. Like Borknagar, Agalloch (most distorted parts are just power chords), Katatonia. ect.