I'm most interested in finding out about Events. Iirc, Events was a theme originally considered for Intrigue before deciding that was mainly a way to add variety and Dominion had plenty. So there must be something more to these Events to make them worth doing. Also, I feel like I might be able to imagine how Reserve cards might work (something like when you gain it, set it aside on your Reserves mats, then various triggers to when you play them?) because they're cards, but I have no idea how Events will even work. Something other than cards (and tokens that just count things) that does something? Now that sounds new and intriguing.
I also hope the previews start to "level the playing field" so there isn't so much tension between the playtesters and everybody else. I mean, some of you might have started playing Dominion years before each other and nobody's making a big deal out of that. The advantage of a couple month's head-start will blow over soon enough imo. I don't like scrolling through negative posts.
Oh and I'm also excited for card names. Will I learn more new words like Mountebank and Margrave? Will the Durations still have a sea-theme? Will we ever get a card named Dog & Pony Show??