I love the base deck - and have been using it for nearly 2 years. I wanted to get the other decks with unique randomizers - so I picked up the Demon Hunters deck for the source material and specialities.
The only real downside to the supplemental decks is the repetition with the base deck - these all feel adjusted from the base deck rather than truly different. Not too much of a problem if you use the decks independently, but it does mean there's only limited utility in mashing them together.
It's still the GMA at heart, it's still wonderful for inspiration or as a tool in the toolbox to help bring in randomized elements or even to drive a whole game from just the cards. I have used these for a couple of one off games - it's so easy to get the outline of an NPC or to quickly get a hook to build a scene off of.
I love the decks, and the minor quibble above does not prevent this from being perfectly useable.
[5 of 5 Stars!]