Any liner notes that offer some insight I didn’t have before and make me learn something are certainly welcomed, not matter what they are. First and foremost, that includes background information about the project (in film music that’s obviously film, but it can also be background information about a particular symphony, concerto, opera, or ballet.
Interpretation and musical analysis, by all means, yes, but with caution, and when it really adds something. As Schilkeman points out, what music “means” is up to the listener, and it should be. Not every film score requires erudite musical “analysis” — most probably don’t — or “interpretation” (because it’s often obvious what the music does and how it does it). Just pick out two famous examples, John Williams’ JAWS or John Carpenter’s HALLOWEEN. The later music is very simply, a keyboard driven ostinato figure, and the former, while undoubtedly one of the most important and best film scores of all time (in my humble opinion), is also pretty straight forward. It’s obvious what the music does in JAWS and equally obvious how it accomplishes it. Now sure, you may inject and spotlight a particular interesting compositional technique, or point to cross reference of motives and themes that may not be immediately obvious, but that is what I often see done in liner notes. Sure, some are better than others, some are more in depth than others, but not all film scores demand equal analysis.
I do have some of the printed film scores that have been published in recent years, not, because I’m such a terrific sight reader, but because I wanted to see — on page — how some of the music is notated… (I always wondered how Goldsmith notated some of the synths and especially the “blaster beam”), so that’s very interesting, but I don’t expect liner notes to include a full version of the printed score. But theses scores certainly offer more of a detailed behind the curtain” look at the nuts and bolts of a particular score than liner notes could hope to give.