I assume they couldn't use Hendrix because of some sort of licensing issue, but Poe was fair game. Making him more central to the story was a bit much but I was sorta okay with that. The aforementioned bit where they screwed up the backstory is 100% the biggest problem. Another issue is the pacing of the climax and ending - not quite Return of the King, but they definitely didn't do a good job with that. The last big problem is what they did with Reileen, which exacerbates the problem where they're turning an antihero into something more like a hero.
Meh. A flawed adaptation of a mediocre book.