Perfect implementation of the Mythic GME system. I currently use the deck solo with Call of Cthulhu 7th Ed rules with the Arkham and Miskatonic University source books as a "logical" backdrop for on-the-fly stories. I also picked up the Keeper decks to quickly pull random NPCs, phobias, and monsters as needed. I can play a deep, low-footprint RPG game on the couch.
Oddly enough, the GME-generated stories with Arkham as a backdrop progress much like the Sherlock Holmes Consulting Detective games, except they are entirely open-ended. The resulting stories and accumlation of clues and locations don't feel random at all. It's kind of creepy (which is great). I'd like to try LA and New Orleans source books next with the GME deck, but I'm currently preoccupied with a growing menace in Arkham.
Perhaps most importantly, the mechanics of the GME deck are fun in themselves. I have some super heavy board games and sometimes the intricate mechanics get tedious to run. With the GME deck, I'm getting intricate, complex stories with mechanics that practicallly run themselves. Every flip of the card is an exciting opportunity for the story to progress in unexpected, yet logical ways, especially when the chaos factor inevitably ramps up.
I don't go as far as journaling with the GME deck, though the scenes play out much like a good movie or book in my head. I use a notebook as a simple date and time calendar as well as investigator's clue book. I track plot points (threads), locations, NPCs, and clues in my notebook as the story develops. It's lightweight and fun.
One little nice-to-have I might suggest is for the publisher is to add a ten step random number generator to the cards similar to Fields of Fire (GMT). As many people will use the GME deck with existing RPG systems, they can dispense with all the various dice and use one or more cards with the random number generator off the deck. Need a D3? Use a card from the deck. Need a D20? Use two cards from the deck. D100? Ditto. Need a D500? You get the idea. It's so easy and compact.