Ilbranteloth
Explorer
What megagaming do you see as a result?
I'd agree with [MENTION=6777737]Bacon Bits[/MENTION]. The metagaming he's talking about is a question as to whether you're focusing on the action in the game, or the rules of the game. We prefer to focus almost entirely on the action, rather than the rules. So if somebody wants to drop their bow and draw a sword in the same movement, it's really a question of whether it makes sense within the present action as to whether we say yes or no. The opposite is a "let's check the rules" approach, which draws you out of the game and into interacting/engaging the rules.
If you adjudicate the action based on the action, then you don't have to think about the rules much. For example, in our game, does the current action/situation warrant advantage/disadvantage, or an opportunity attack? If not, you just continue with your normal attack and damage rolls, which require very little interaction with the rules. On the other hand, 3.5e and 4e had all sorts of combinations, actions, and circumstances that would allow bonuses or penalties to hit, etc. And they often required more math to accomplish, so you're drawn out of the game-world action to the metagame, that is, the things in this world that make the things in that world possible.