Its a natural fit for artifact-heavy decks, where artifact token makers or resilient pieces like Darksteel Citadel become huge threats that swing in every turn
The flexibility of being able to choose a value for X is great because we might have an early-game case of wanting (or needing) to cast it for X of one or two, or we can wait until late-game and sweep a much bigger battlefield
But what it doesn't do is tell you whether the card is good, valuable, or worth building around
The blue creature Maeve, Insidious Singer has a very silly name, and uses Wizards' new favourite Commander mechanic, goad
Electrodominance Gruul is a uniquely good color combination for big mana burn spells
, : Put target creature card exiled with The Darkness Crystal onto the battlefield tapped under your control with two additional +1/+1 counters on it