I never finished any of these on my own, 'cause in those days, you had to buy the "invisiclues" book with invisible ink pen, and those cost real money. I can only guess I was given the games as presents, as I couldn't afford those either. But I did play original Zork, Hitchhiker's Guide to the Galaxy, and Leather Goddesses of Phobos. The Infocom games had all kinds of swag in the box - LGOP had an actual 3D comic book about Lane Mastodon (space hero, thwarting the evil intents of the Leather Goddesses), with 3D glasses, for instance. HHG2G had pocket fluff and a button and brochures. That kind of thing.
They were fun enough, but in all cases, I eventually got stuck to the point where I couldn't continue because I didn't know what to do next. So I'd quit and go do something more enjoyable and less frustrating, so I never finished the games, since I got tired of beating my head against it and never getting anywhere. ^^;; Nowadays if I ever try 'em again, I'll have a GameFAQs walkthrough in a second window. It would be nice to finally finish one, eh? ;)