I thought the soundtrack was good on it's own (I love Ben Prunty's music), but it did not fit the game.
The way the music and audio design in-general in the first game all fit together so well is what made half the experience.
And yeah...
::: spoiler spoiler
you go down to find out what happens to your sister, then that becomes a side quest you can forget about and you fuck off with a random alien :')
:::