So, I want to address power creep. I think for the purposes of Dominion power creep can be defined by how often a card is bought and defines a kingdom. For example, Goons is a very powerful card. You buy it almost every game it appears in.
I also think Qvist's rankings is a good way of looking at how powerful an expansion is overall. Obviously, the rankings for Adventures will change a lot next year. But, with that said, Chapel is obviously the best trasher. Mountebank is the best junker. Cultist is close though. Ambassador is the best $3 cost.
Someone said that Adventures increases the power level the same way Seaside did. I think perhaps Events might make this somewhat true. Attack-wise, though, I would say if anything, this set is a decrease power-wise. The attacks are decent, but we have seen nastier stuff. The trashing is good, but, DA offers strong trashing as well and Chapel is still the king of trashing. One area, I do feel Adventures increases the power level is Villages. Overall, Villages are often needed to make engines come to life and with Adventures, I feel, we get the strongest Village ever in Lost Arts. Champion is obviously stronger, but takes a while to get going. We also have Coin of the Realm, a village that we can use when we need it, and hey, it's technically two villages when you call it into play. We have had strong villages in the past with Fishing Village and Wandering Minstrel. Lost Arts is simply better than them. And, once you get Champion going, well, boom. Also, Disciple and Teacher are pretty nice villages as well.
Card draw is also pretty good in this expansion, but not super common. Pathfinding can be the king of card draw if you have a good target for it. Sometimes, though, you might already be drawing your deck, although, pathfinding a card tends to add more reliability. We also have Haunted Woods. It's strong card draw, but not as strong as Wharf.
I think overall, kingdom-wise, the cards are pretty balanced. We do have two power houses with Page and Peasant. But, I would say more than anything, Events are what shake things up the most. Alms guarantees you always have $4 available. Save can do tricks and then we have the token events that modify piles.
I guess the real question to ask ourselves is what would Dominion be like today if Events had existed since the beginning.