Broken Base: Let's just say that opinions on the anime differ drastically.
Hilarious in Hindsight: Maharl claims to be Krichevskoy's daughter and Laharl's sister and is planning to take the throne. Fast forward to Disgaea Dimension 2, in which Sicily, an angel who claims to be Krichevskoy's daughter and makes an attempt to take the throne from Laharl, is introduced. Unlike Maharl, however, Sicily is Laharl's sister.
Love it or Hate it: You're either fine with the changes and enjoy the anime, warts and all, or you find it a bad representation of the source material and think the quality is unforgivable.
Memetic Mutation: Due to the differing quality between the trailer and the final product, fans love to joke that the animation company blew their entire budget on the trailer.
Part of the problem that many had with the anime was that it's original trailer had far better animation and seemed to be a lot more faithful to the game, even hinting that Baal would appear. The final product was sadly plagued with Off Model animation and while the general plot was the same, there was enough changes to put off several fans. The lack of any real fight scenes only served to hurt the anime.
One particular change that put off a lot of fans was the ending, which tried to combine elements of the game's Normal and Good Endings. While interesting in theory, it made Lamington look like a Jerkass who planned for Laharl to commit suicide all along and the lack of Character Development between Laharl and Flonne (Due to the anime being more focused on comedy) made Laharl's sacrifice rather jarring.