Any reccomendations of any bands that use piano/keyboards well?

I don't like Dimmu Borgir very much, but I agree that their use of keyboards is one of the band's high points.

Check out Ajattara -- a heavy sideproject by Amorphis singer Pasi. It's like Emperor at half-speed, or a more atmospheric Celtic Frost. Highly recommeded, especially the Kuolema album that came out this year.
 
Limbonic Art's "In Abhorrence Dementia" contains some simply ethereal keyboard-playing, so you definitely can't go wrong there.

I would also recommend anything by Dream Theater, particularly on "Awake" and "Images and Words," as well as Antimatter, Burzum, Amorphis(especially on "Tales From the Thousand Lakes"), and And Oceans...
 
Metal Bands With actual keyboardists: Dream Theater, Nightwish, Symphony X, Rammstein [Not as technically proficient, but very well-written]

Not Metal but insane all the same: Yes [or Rick Wakeman], Emerson Lake & Palmer [or Keith Emerson]
 
SAVATAGE!!! Jon Oliva is the KING of the metal keyboards/piano! Check out their albums, "Gutter Ballet", "Streets:A Rock Opera","Edge Of Thorns", "Handful Of Rain","Dead Winter Dead", "The Wake Of Magellan" and "Poets And Madmen".