You get to draw an extra card, re-spend all your mana, and get an extra combat stepnot to mention extra upkeep/end step triggers, planeswalker activations, and so on
Its a nice contrast to the usually beastly, large, rough animalistic Forest and green cards were so accustomed to
The -2 also circumvents expensive mana requirements by cheating an artifact into play for free and offers a bit of recursion if one of your equipment gets destroyed
So long as you can stall the game (perhaps using board wipes to get creatures into the graveyard), youre golden
Florian can dig super dip with his ability in this deck
If you have more than one commander (thanks to a partner ability, for example), controlling one of them when you finish casting Ancestral Communion is enough to satisfy the trigger condition of Ancestral Communion's first ability