I'm about to download it but I notice it's 1.6 GB...yikes....Is it worth the long wait to download?

Interesting NPCs is extremely well-written and well-acted. I think the voice acting is as good, if not actually better, than the voice acting in the vanilla game. I think the writing, too, is usually better than the writing in the vanilla game. Be prepared for some lengthy conversations. Some of these NPCs talk for ten minutes or more.

If you like to play characters who wander around and talk to NPCs I think this mod is worth every megabyte of its 1.6 gig download. But if you plan to play an anti-social character who doesn't talk to NPCs very much you might be better off with a smaller NPC mod.

Hell yeah! New followers, new dialogue, new voice actors, new quests and new music. Much better than vanilla and some it OMG good.

Good support from the mod author too.

What about vampires? Is there any vampire companions? I'm wanting that the most.

The voice acting might be good, but the sound quality is so so IMO. While I appreciate the amount of work that has gone into the mod and think it seems to have high quality overall, I personally find it immersion breaking rather than the opposite. The added NPC's tend to stick out, i.e. I saw immediately that "hey, that must be a char from Interesting NPCs". Plus I found the sound quality less than stellar, albeit that is with the random bunch of NPCs I've "tested". In short, I've actually tried it twice as so many are so enthusiastic about it, but both times I skipped it shortly afterwards because of the above reasons.

That said, it's also throwing pearls at swine in my case, as I've never been that interested in listening to NPCs in the first case. I tend to fast-forward if possible.

It is, as you would expect, interesting