Having listened to the album a few times and seen the film once, my initial impression is...not great. There are some strong moments, but overall this probably the weakest John Williams Star Wars score in my view. The main reason is there was far too great a reliance on existing themes and cues. There are so many characters in the Star Wars universe, that the impression I got was JW (or perhaps Rian) was using every excuse he had to lean on music that had essentially been written for the previous 7 films. "Oh this scene involves Leia, let's essentially cut-and-paste from her concert theme. And now the Resistance is fighting, let's do the same for them. Oh look, Leia is talking about Han, we'll have to use their love theme." And some of the pasted material doesn't really make much sense (I won't say which to avoid spoiling anything). As many have pointed out, the end credits piece is hopelessly scatterbrained.
The best piece is by far "The Rebellion is Reborn" which is very strong. The best new theme is the one for (I think?) the Resistance that shows up in "Rebellion is Reborn." Although I think it might have been better suited to represent the prequel's Republic - it sounds very regal and tragic to my ears. And I must say, the fact that JW is able to lean on his preexisting work is a testament to the incredible library of themes he has developed over the decades. He could have easily written a passable score without creating a single new theme.
I was not blown away by TFA, but at least there was a fair amount of newness and cohesion there. Maybe TLJ will grow on me overtime, we'll see. My hope is that this is more a result of Rian Johnson's direction than JW's (lack of) inspiration with the saga. If so, perhaps Episode 9 will be more inspired.
And for the record, I love the prequel scores and think they easily stand shoulder-to-shoulder with the original trilogy.