I don't know how I feel about Nxt being described as a metacoin, but since Ethereum is also on the list, it's not so bad. I have noted that Andreas has mentioned Nxt a few times as "a layer on top of Bitcoin", though, which bugs me.
"Metacoin" in my mind is a coin that is designed to have other coins or assets ride on top of it. Mastercoin is what I'd call a layer 2 metacoin bootstrapped on a level 1 coin. Ethereum is a level 1 metacoin, Bitshares is a Level 1 metacoin, and NXT is a level 1 metacoin