"The band broke up before fully realizing their potential,"--Sorry but are you high? Soundgarden were together for 12 years and made 5 seminal, genre defining albums and several lesser known (but brilliant in their own right) eps. I agree that they went out with a bang, with an album that held up well to any of their previous masterpieces. But to suggest that they never reached their potential, simply because they broke up at the peak of their popularity, is nonsense. I would agree that Audioslave was not at the level of Soundgarden (though still a great band) and Euphoria Morning is the only solo album that is on the same plain of quality as his best work with Soundgarden. But as a band, Soundgarden accomplished everything a musician could hope to accomplish--in terms of both commercial success and artistic accomplishment. That they are releasing another album after all of these years will be icing on the cake--provided that the new material is on par with the rest of the bands creative output, of course.
I really respected Soundgarden's decision to break up when they did, not because of personal problems in the band or a tragedy, but just because they didn't feel like they could do anything more than they had. I wish more bands would do this instead of just milking it years beyond their prime. But 15 years later I'm glad to hear more music by them, especially since there have been very few good new bands since they broke up.
I don't agree that all their albums were equally good -- Superunknown broke through to a richer sound which they never took further.
I respect that they were tired and needed a break, I'm not saying they should have kept on if they would have just been going through the motions, but looking back now, it seems possible that they could go further rather than just recreate their sound of 20 years ago.
I read an article once about why they broke up (of course, I can't find it now)... They were opening for Guns N' Roses, during the Illusion tour, and they saw all of the theatrics (piano rising up, backing symphony, etc.) and they were like "is this what we're headed for?" And that's when they decided to call it quits... I wish I could find that "quip" again...
Right now, you can stream the new album for free on iTunes. It's a straight shot through the entire thing, and I've listened to it twice so far. IMO, it's amazing. It doesn't sound like any of their previous albums. If you're like me, you listened to their Avengers track and single and wasn't that impressed. But trust me...the full album is awesome.