This seems like a very powerful option for non-blue Gx decks such as @ChubbyRain 's Jund deck, and for UGx Xerox decks.
This card seems great for the format because it does not actually give you card disadvantage, and it allows you to come back from a very prisony start for little to no cost. I like the fact that it makes you play green as it is not a very played secondary color (mostly a tertiary color) and I think this could very easily change that.
The fact that it is 2GG makes this card a bit less likely to be realistically hardcast and if you do then you are likely very far ahead anyway. In my opinion that does not really matter and this will be a very good SB card for many decks with some playing 1 or 2 main.
Also, this with Force of Negation seems to suggests a cycle of "force" pitch cards for each color, doing something that each color is known for.
As a Dredge mage I am very very excited for this Force cycle since so far both seem very powerful in a Dredge shell. Dredge lives off of free cards so the ability to have free counterspells against hate and free removal spells seems insanely attractive, additionally since both new Force cards are instants you can use Force of Negation to protect Force of Vigor. I am excited to see how Dredge changes with these new card.
So far I very excited and happy with the new set as it seems to provide very versatile but not overly powerful cards.