The Character Died with Him: Averted. Igor's role is diminished because of the death of his Japanese voice actor (Japanese tradition is to retire characters when their voice actors pass away rather than recast), but his archived dialogue from the game is still used to keep the character in the anime.
Playing Against Type: While the dub makes her more expressive, it's rather unique to have Cassandra Lee, who normally plays characters more impulsive and emotional, playing Aika, who is stoic, calm and rather serious.
The Resolution Will Not Be Televised: The TV broadcast only covered up to the "Good Ending", which deals with the confrontation with Adachi and the battle with Ameno-Sagiri. The REAL final episode, titled "No One Is Alone", was released with the tenth (and last) volume of the anime in Japan.
One of the things that convinced fans the series wasn't going to be a half-assed adaptation was the announcement that the entire cast of the game would be reprising their roles for the series. This even goes so far as to reuse Igor's dialogue from the game, due to his Japanese voice actor dying in the time between Persona 4 being released on & the development of the anime, rather than recasting the character.
The dub follows suit, to an extent - the majority of the cast returns, albeit with Johnny Yong Bosch altering Adachi's voice to sound less like Yu Narukami & the examples mentioned in The Other Darrin above.