I need to stop jumping in here and defending bands, because it just feels wrong.
Anyway, I think Nirvana was an incredible band, In Utero is an amazing album, and I don't think they're overrated at all. I think as time moves on, I hear the opinion that Nirvana is overrated more and more often (I'm not saying you're saying this at all Magrao), and I think I just want to say that I don't think that's fair. They deserve the acclaim, not just for the awesome music and their undeniable impact on everything, but also what they did with the exposure afforded by their popularity. They were a great band.