Going from a Newstead thread to a Metallica thing....
It amazes me that people the last few years have continued to say that "Metallica sucks, they have sold out, if they cared about the fans they would play only old stuff, blah blah blah". The point I think these people are missing is that over the years Metallica has grown and matured as a band, and their music is naturally going to change because of that. If you are loud and aggressive all the time then people will tend to lose interest.
Take bands like Slayer for example. They have played the same type of music their entire career, and they have made a living off of it, but they still do not have the wide ranging audience that Metallica has. I don't think that Slayer has had a Platinum album to their credit yet, and I think the last 3 or 4 Metallica albums went multi-platinum.
The point is, in order for a band to stay vital, they have to grow and evolve musically. If you play the same thing all the time, people get bored with it and stop listening, because they have heard it before. There are plenty of loud and angry bands on the scene now, so Metallica does not have to do that anymore. They can stretch out and do other things, like the S&M album. So, go listen to Kill 'em All when you need aggression, and then listen to S&M when you want something different.