I played the game at Expo and the audio / speech didn't bug me at all. I really liked how it flows and how smooth the elevator was working.
The only (general) suggestion I'd like to make in terms of speech is to use some sort of audio compression to really have the speech come out. The Dutch Pinball guys have that in BOP 2.0 and the speech doesn't get lost in the background music. Other (P-Roc) games didn't have this and made it hard to understand what was being said.
Although I played a couple of games I don't remember if each of the ghosts have their own theme music. If not, I would strongly recommend that.
Another (general) suggestion I'd like to make: it may help if certain playfield areas would have a standup plastic (or playfield indication) with some text (and an insert/LED) to help clueless players (like me) why/when to shoot a certain shot.