I had this back in the day, just played the first few mins of the GOG version. Noticed that the background music is different, the first policeman dosn't say "for christs' sake" when he blows up like the original and the cigarette machine says different things (my version it used to say "The Surgeon General's a fool". Any idea why? Mine was the UK release so maybe it's a regional difference.

Having just finished my first play through of the GOG version I can tell you the audio is very glitchy. The scenes you mention played fine for me including that dialogue, however, at other points in the game I'd have missing dialogue, music and/or sounds. There was quite a long cutscene later in the game were the sound cut out leaving me with no audio at all and the club level near the end also had no music, which looked a bit odd with everybody dancing.

I'm in the UK too, so I don't think it's a regional problem - more of a really buggy game issue. It also crashes a lot at certain points so I'd save often if I were you.