In Commander, where players have access to so much fast mana, this is potentially a death sentence
It changes the math of each turn enough that it requires some double-checking and re-evaluation, which can be a little frustrating for a new player who is still trying to figure out what their cards do
You don't have to choose every permanent or player that has a counter, only the ones you want to add another counter to
if you transform Emet-Selch too early, you run the risk of running out of cards in your graveyard before you can defeat your enemies
The set itself contains a whopping 1,694 reprints from all throughout the game's history (see below for the full list), plus 121 copies of something new and surprising
It isnt really broken, but it changes up the pace of the game to allow a unique and consistent form of ramp for green