Definitely a step in the right direction, but with room to improve!
The original duels was a pretty solid game, but it had it's problems. Large imbalance issues with the DLC, online hiccups, Not very much customization, and.. though it matters little, the UI was rather ... dull.
Duels 2012 improves on all these issues. With core deck editing, you can keep your decks down to 60 cards, or just keep all your cards in. There is even a little stats index for each deck to tell you how much of what cards you have, etc. it adds quite a bit of customization to the game, very reminiscent of the table top game.
As far as balance goes, there are a few decks that are clearly "top tier", but even they are weak against certain other decks. No one deck really trumps them all (like how Master of Shadows clearly broke the balance in the first duels).
And of course, the UI is completely re-done, and it looks pretty good for a low-er budget game.
That coupled with the new ability to play co-op online, as well as the new mode "Archenemy" (which can actually be extremely difficult), makes for an amazing game, especially for a mere $10!