I'd like to say that I agree that while all of the new tracks are awesome, the new guitar pieces do seem a bit incongruous with the rest of the soundtrack. That's not to say that they're not good, especially the new 'Thor' (bits of which remind me of some of Mike Oldfield's work) and 'Metal', but it is a bit jarring when you're listening to piano and strings and suddenly you have this bass guitar, which, while well-played, is still something terrible to spring upon the unsuspecting. What I liked about the old guitar pieces was that they blended in better with the rest of the soundtrack. They were more exciting, but didn't 'stand out' as such.
Perhaps the problem might be solved if there was a way of playing the more 'active' tracks only when there is a major battle?