Pros
-Easily searchable with level ball, emolga.
-Can deck out your opponent.
-Can disrupt your opponent by discarding crucial cards from their deck.
-Colorless attack (not that you'd ever use it)
-Only needs 1 energy to retreat or mill.
Cons
-70HP makes it easy to kill.
-You need at least 3 out to put any real preasure on. (good luck if one of them is prized)
-You may end up helping your opponent by discarding cards they don't need (or cards they want in their discard pile).
-Deck is slow.
Overall. If you make a deck devoted to mill, it can be annoying, but it requires a good setup. Even then, once your opponent gets an attacker set up, they are six turns away from victory. Probably the best mill card in the game, but it's still not the most reliable.
Overall: 6/10
Artwork: 7/10