For example, it can't be used during the resolution of an ability that says "Counter target spell unless its controller pays ." (2/9/2017) If an artifact you control has a mana ability with in the cost, activating that ability while casting a spell with improvise will result in the artifact being tapped when you pay the spell's costs
Reclamation Sage is a classic ETB Naturalize effect to get rid of enchantments or destroy artifacts, and has the elf subtype, which can be relevant in elf typal decks going forward, or even in the sideboard of green decks in general
It's a more powerful battlefield and built-in protection from an Edict effect targeting you
For example, the Human Torch's ability takes the combat damage he does to an opponent and applies it to every opponent, whereas The Thing can double all counters on all permanents
Instead, Flower is a must-include in just about any Amethyst deck for its ability to filtre through your deck at lightning speed