My favorite game system by a mile. I love the structure of the deck, the double suited cards as well as the assymetrical distribution makes for a very unique set of cards. This makes for some very interesting trick taking games but it also works well for area control, it opens up a lot of possibilities.
The art work is phenomenal in both decks although I prefer the Capital Deck. I do find myself distracted at times during games looking at the art work, spotting curious little details in the scenes. The Decktet book is a great add on to the decks if you are drawn to the system, it has a lot of information on the deck itself and rules for tons of games.
There are a number of good games for the Decktet, some of the more notable ones are Magnate, Jacynth, Emissary, Emu Ranchers. Personal favorites (besides the above) are Adaman, Double Knot and Goblin Market. And there are loads more that I haven't even tried yet!