Gengar has a +30 weakness to dark type Pokemon, a -20 resistance to normal Pokemon and a free retreat cost
you get invaluable information on how they intend to curve out and get to play around cards, especially situational ones like Daze that are much worse when you know about them
The biggest area I currently struggle with is graveyard hate
an old game store in Gothenburg
We can also use Wrenn and Seven or Nissa, Vital Force to return permanents from our graveyard to our hand, which can lead to some really weird legend-rule loops where we play multiple Ugin, the Spirit Dragons or Nissa, Who Shakes the Worlds, use their abilities, with each copy legend-ruling away the first, return them all to our hand with Wrenn and Seven, and eventually kill our opponent with Ugin damage or a massive Nissa, Who Shakes the World land (which gets especially massive thanks to the extra counters from Doubling Season)
But even larger runs can be costly