Not bad. As someone else mentioned, formal writing is meant to be in the abstract third person, so maybe you should think about changing your use of 'we'. Also, be careful with what you say about the fans of the metal genre, as, even though i pretty much agree, this is meant to be impersonal ("While legions of corpse-painted, spike-adorned Darkthrone purists may declare Opeth sellouts for daring to toy with tempos under the 380 bpm mark"), and so should not contain irrelevant opinions such as this. Oh, and someone please correct me if im wrong, but im pretty sure melancholy goes to melancholic in the context you've used it in (2nd para).
As for the actual writing itself, though its clear you love to write about this, try intersperse your writing with the occasional simple (short) sentence, or the reader is easily fatigued, ESPECIALLY with such heavy usage of such descriptive adjectives (and adverbs). If you are going to do any re-writing, I would actually say that the first two paragraphs really constitute a long single intro, and could perhaps be merged, which would then give you more space to spend on your 'nuts and bolts' of the review, paragraphs 3 and 4. It would be interesting to hear you say something about the themes of the songs, more about the meaning behind the lyrics, 'context' in terms of past albums an interesting point (this was a concept album, and i dont think you have even mentioned this). This is a review by the way, so even a little more time spent on each song would not go unappreciated.
Lastly, the conclusion does need work. Dont end with such a biased line as you do about Limp Bizkit; you are reviewing Opeth, not Fred Durst. You open with an unsubstantiated declaration that it is not their finest, the explanation in brackets doing little to justify it, and this needs to be changed. You also suddenly proclaim that they do not fit within the 'modern death metal' sub-genre, whereas you haven't actually previously said that they ARE death metal; i dont actually see any classification anywhere. And finally, it is interesting that you say "This isn't simply good metal, this is good music, period," and then continue the sentence - the slang use of the word 'period' aside from being a questionable inclusion into formal writing, should end a sentence, not appear in the middle. I hate to be niggly (well, actually it is kinda fun..), but I've had too many essays marked down for annoying things like these not to mention it when asked.
Hope this has helped, and would love to read it again if you do do any substantial editing!