They are pretty noisy and downright heavy, I agree. But the reason they are good is because there's just something very unconventional about them. Nile simply isn't typical death metal. The Egyptian influences are where most of their melody lies, but as far as pure death metal goes, they are quite art-y. They use keyboards for atmosphere every now and then, as well as certain Egyptian instruments. Very innovative IMO.
I can't say they are an all around incredible band though. Sometimes their brutality gets in the way of their musicality, but not so much so as with most death metal bands.