Spiritualist is my new obsession. I am in love with this class from a design space, as well as from a flavor space. It hits every note I want, with only a minor oversight - the ability to directly interact with your channeled spirit as if they were there in person, like a familiar or a different NPC - that is easily handwave-able by any DM or player wanting it.
I've been playing since 1995, and my favorite class from the TSR DnD era was the Shaman. I've tried to find a way to represent that class over and over again in the later editions, and nothing hit the mark. Spiritualist hits that mark perfectly for me. I am also an avid player and DM in the Ravenloft setting, which this class plays into absolutely perfectly.
I love the use of Pact Magic, it makes perfect sense flavorfully as a channeler of the spirits. I love the subclasses being story oriented choices, that really implies who your character is or what they have gone through; mechanically, I love the variance in the subclasses as well. I've found my favorite DMsGuild classes are ones that provide a solid framework and the subclasses can all play drastically different from each other, and Spiritualist perfectly hits that button for me.
I implore everyone, get this class. I am dying to play one, I have a player with an old 2nd edition character waiting in the wings to come back as one, and have already converted an important NPC to one as well in my home campaign.
[5 of 5 Stars!]