There was a lot of "OMG I'm almost dead"-ing going on. The enormous attacks flying around, even at first level, mean characters are often bloodied by the end of the first round, causing them to use their Second Wind right away and spend the rest of the fight biting their nails afraid of another big hit. Buzz, the reality-shifting "doppleganger" NPC kinda-sorta did die, but that ended up being in a reality that collapsed, and a completely-healthy version of him came walking in the door. (Mechanically, he made his "save vs. death" and the rest was just extemporizing on my part based on his background.) Downshift, hantamouse's android, also went down near the end of the session in an ever-replenishing robot factory floor, but held on thanks to a successful save.
I don't know how sustainable this is going to be once the initial scenario is done. Even with some booster packs of cards, there is so much flux going on all the time that it's hard to get a feel for a character -- and it's also hard to get a handle on just what people in this setting might care about. It's not a setting that bears up well under examination, but without being able to examine the setting, how do you come up with interesting scenarios for it?
Still, since the characters are likely to reach 2nd level by the end of this adventure, I might hunt up a 2nd-level 4E adventure that seems suitably re-skinnable and see what I can do with it, if I can find one that has a core concept more interesting than "There's an evil cleric at the bottom of the dungeon, go get 'im." I've got all those PDFs of what WotC insists is Dungeon magazine (no, it isn't), maybe I can find something there.