Celestial is one of my favorite releases EVER. Its just about the heaviest thing out there. Not heavy in a brutal way, but in a wall of sound/emotional way. I feel they use melody and dissonace the same way that Opeth does, albeit with a far different outcome. Get any of the songs from the Celestial CD if you don't just go out and buy it. I seriously can't say enough good things about them.
Some other bands that are like them: Cult of Luna (sweden), Breach (sweden), Old Man Gloom (well, its pretty much the same band, heh), and Cattle Press to some degree (only with a black metal influence).
Celestial was released via Escape Artist Records. The newest CD was on Neurot. And the forthcoming one is going to be on Ipecac.