I'd say power chords are still useful en all, don't give up hope just yet.

Try listening to different bands and see how they use them to change the over all style of the song. Iron maiden uses a galloping technique, while metallica has a wider vareity of uses with them. alot of megadeth songs feature this one technique where u kind roll/circle the pick in an arc, to get a cool effect.

or

you can try some other cool effects
like what i call the backwards powerchord fig 1(Dsus2 ) (check out songs on metallica's master of puppets and ...and justice for all,)
--fig 1----fig2------fig3---fig4---fig5-fig6--fig7--fig8-
b--------------------------8------------------------
g--------------------------7-----4---4----6-----10-
d-5 ----------5----- 7-----6-----2---5----0------7-
a-7------5-7-0------x-----7-----3---3----7------8-
E--------0-0--------5-------------------- 5-----10-
or try the whole open string effect( fig2 variations of Dsus2), it can be heard in songs like unforgiven for the verse riff. sevendust uses it alot too

*unforgiven - by metallica*
------------------|-----12-12-11-11-----------|
-12-10-9-10/9----|-----0--0---0--0--10-10----|
-0---0-0---0--10-|-x-x---------------0---0-x-x|
---------------0--|-x-x---------------------x-x|

or a good harmonizing effect like (fig 3) where ure holding down on 2 'A' notes. Sounds real cool when used rite.

Even with alot of distortion dun be afraid to use funky chords. Check out war pigs - by black sabbath they incorporate the hendrix chord fig 4(Em9) - it really changes the feel to the song.

Or try chords like fig5(E/C) this sounds real good. I guess alot of bands use it but i first came about it when learning 'frogs - by Alice in chains' (or was it sludge factory, cant remember) back in 1997, but its used alot in softer stuff like drive - incubus.

Another thing u can do is check out bands like 'at the drive in', 'sparta' and 'the mars volta'. I know they delve alot into a certain punk vibe, but they sound heavy whilst barely using any powerchords. (its been a while since i listened to em so dun hold me on that one).

..shi*... my TA's back, freaking summer skool...!%!$%@$%@$$&%$*...f*** EELAB ****

i hope some this helps, its totally off memory so i appoligize for the inaccuracies, and ignore the typos , i'll edit this when i get back home

late