After using sites like rpgsolo and the Mythic gmemulator for GMless play with my brother I found myself stumbling onto these, with the hopes of using them on Roll20 via the deck system, thanks to Larcenous Designs Nathan Rockwood's very helpful support post-purchase, i've been able to do just that; It's worked great.
The sheer amount of content each card can produce is huge, and I personally find it much easier and quicker to create an event or reaction using these than other systems.
The runes are my favourite part, they really make it easy to come up with things quickly and avoid the game pace coming to a crawl (Something I found happened with gmemulator when you had an event or detail randomised and just drew a blank on how to interpret it)
GMA gets around this problem with a number of additional ways of clarifying or adding detail to events. It is exceedingly easy to quickly piece together everything from a world ending threat, the motivations of a villain or even just the traits and attitude of that barrister at Starbucks!
Easily tailored to any game system or theme with massive amount of variation and detail available for anything you could possibly need for a smooth and exciting gm-less game!
(Currently using my sets for a Mutans and Mastermind's game and a Pathfinder game)
[5 of 5 Stars!]