I have played through the beginning of this game and I have noticed a few oddities. While examining some objects (like the picture of Blob on Curtis' desk), text just shows up on the screen telling me what Curtis is saying. I have played and seen other versions of this game and in those, Curtis speaks aloud the words that are being shown to me. Is this dialog supposed to be missing in this version?

This does sound quite like a bad issue, my download is at 80% and I'm gonna check this out when I can play the game. I'll address this a bit later.
It DOES seem there's something weird going on, Curtis won't comment on anything verbally, the only time there's audio is during FMV. Need to hear about this from the GOG team.

I'm getting this too. I played the cd windows version when it was released and there was definitely audio on these areas.
In the GoG version, clicking blob's picture, or dialing various people on the phone in curtis's office results in text on the screen when it should be playing audio. Kind of weird, but limited mainly to his cubicle and not much of an issue.

I'm just guessing here, because I haven't seen the other versions, but I would find it weird that GOG would remove dialogue and reprogram text to appear in those parts, so it must be original version they are using which has the dialogue missing.
adamb171 said that speech appears in Windows version, but GOG is using DOS version, so maybe it's DOS version feature that there is no speech on those parts.

Ah well, that is a real shame.