You can ping your opponent to death on the turn you cast Niv-Mizzet using this combo or, combined with sis crawler or Laboratory Maniac, you can win as you draw out your deck
It is effectively card advantage in decks aggressively going for life totals as well as impressive tempo
Her power is equal to the number of creatures you control, meaning she often enters the battlefield as a massive threat even without external buffs
If you do, put another target card from your graveyard on top of your library
Gates is very much a five-color strategy, and while Nine-Fingers Keene is great in those decks, it should not itself be a commander
Perhaps the best thing you can say about Tendershoot Dryad is that by itself, with no other token support cards, Saproling synergies, etc., its still a super-dangerous, must-remove threat