I am a bit of a Steve Albinin fanboy. I never miss Shellac when they come to town and I will always give an album he recorded more of a serious listen than if he wasn't involved.
I'm no much of a Nirvana fan anymore and this letter really doesn't say much about Nirvana at all. http://en.wikipedia.org/wiki/In_Utero_%28album%29 has some interesting background about the album, which they gave to remix masters in the end anyway.