To add to that, it's a creeping rules lawyer thing - Dominion is now a game where you can physically draw a card from your deck into your hand but you didn't "draw" it, put something into play without playing it, and add things to your discard pile without discarding them (that last one was always possible). I normally detest that sort of thing in a game, but in Dominion it's been slow and earned, so I don't mind.
But it's something to be aware of, because the casual player will listen to you explain why you didn't actually play that Reserve you have in play and pronounce the game "stupid" if you're not careful.