Hi -- I'm Joe, and I'm a community manager at Gearbox. We got lots of feedback on the way the voiceover was syncing, so the team went back and made some pretty big improvements that will be coming to the game soon. You can see a video on the Bulletstorm blog that shows how far its come: http://bulletstorm.com/blog-en/make-it-rain-bullets-bulletstorm-full-clip-edition-has-arrived/
All that said, I hate that the game didn't quite hit the mark for you, but we genuinely appreciate your feedback on this!