Lots of fun. We had three players who had played it before, one who knew the Marvel stuff but hasn't played any deck-buildings, and I practically knew the mechanics from the similarity to Dominion - and it was equally enjoyable for all of us. It's one of those cooperat-ish games where you all lose together, but if you work together to win, one of you wins "best" and the others still lose. So, naturally, I got to throw the game as soon as someone else was about to take it all.* Never play cooperatish board games with me, apparently.
* It was the second round we played, and this was after a certain game of Arkham Horror where he made sure everyone else was moving through R'Lyeh before winning the game without us. I think we're even now.
I haven't played many deck builders at all but it had good unique play as far as I'm aware. I'd get it myself if other people would play games with me
EDIT: Another thing I like about this style of games is that the majority of the rules is found on the cards - same as games like Killer Bunnies or Munchkin. Helps new players get in without an hour of explanation of how