I very much enjoyed the read of WtO, but by the time I read it I had a little Vampire the Masquerade under my belt and I immediately recognized that the game was unplayable as a role-playing game as written. Those groups that I know to have gotten into Wraith (and latter Wraith supplements) adopted a style of play and story radically different from the one which was implied by the original source book.
WtO takes as its inspiration classic stories of hauntings. WtO as it was actually played was closer to D&D: Planescape. There are multiple problems with playing out hauntings in an RPG.
1) In a classic haunting story, everything truly important in the character's life has by definition already happened. The character has no life, and instead are stuck in a limbo and doomed to repetition on a theme. This greatly constrains freedom in a way that makes extended RP difficult. Once you play out the theme once, then what? Growth and change are difficult, and multiple arcs of growth and change difficult to conceive.
2) In the classic haunting, the dead character lives out his story in relative isolation. Classic haunting stories have one ghost, and possibly multiple people being haunted. Interactions between ghosts are rare and confined classicly to reliving the past. One of the biggest problems I see in well written RPG material is the failure to consider how the game plays out with multiple player characters. You simply can't expect to play out a haunting scenario with a group of ghosts with widely different backgrounds and differing motivations. Successful RPGs develop around the concept of multiple players. Moreover, successful RPGs in practice need to have the concept of multiple players and only one NPC with a speaking role at a time. In practice, an RPG can't depend on and should generally avoid multiple simultaneous NPCs on stage with a speaking role, because what you end up with is too much burden on the storyteller and too much tendency for the players to be mere witnesses to the entertainment.
3) In the classic haunting, the dead character's ability to interact meaningfully with the world (the world of the living) is highly constrained. WtO actually attempts to model this to varying degrees and does a fairly good job assuming the players adopt a role-play centric as opposed to character optimization approach to character building. But the result is a very slow pacing to the story that requires a very skilled DM (it's actually well suited to a bang approach in my opinion).
In short, playing the WtO coming from a D&D background is very difficult and likely to be very unsatisfying. In practice, the WtO stuff I know about largely ignored the mortal world and the character's past life and everything the source material considered fundamental and instead played otherworldly superheroes games. This is much like what actually happened with most VtM groups in practice.
My pick for the best written/most dysfunctional RPG would be 'Monsters and Other Childish Things' which is probably the best written RPG of all time, has great mechanics, and is utterly and completely unusuable in your average RPG group. The problem with the game is principally that all the fluff of the rules set focuses on the interactions between a single player character and a ubiquitous NPC (his monster). Other children with monsters appear in the text almost entirely as foils and usually are 'offstage' in the fluff text, where the interaction is being referred to as some thing in the past rather than interacted with in the child's present. No apparant thought is given to how the game would play out with say 4 or 6 children having 4-6 ubiquitous NPCs (their monsters) plus whatever NPCs they are interacting with. Imagining this scenario in my head gives me as a game master a migraine. All of the really cool internal intimate monologue that makes reading the rules of MaOCT so cool is impossible under these conditions. Actual interaction between the child and his monster (played by the DM) has to be more or less pushed aside to prevent a player from monopolizing the DM's time. The web of personal relationships that the rules so cleverly implement in a hard mechanical fashion must be pushed aside in favor of dealing with the intra-party interactions, because frankly, the game gets boring if everyone has to go home to their mom and act out their intimate family relationships in turn. In such a game, each relationship is largely now offscreen and instead of there being a deep connection between mechanics and RP, the relationships become just another mechanical resource. And as a DM, I shudder at the idea of having 4-6 (or even let's say 3) complex NPC's with various traits, individual motivations, and important parts on stage at all times.
Both WtO and MaOCT in my opinion can only really be played as described with one DM and one player. However, relatively few people are comfortable playing in this fashion especially given the emotional content (compared to hack n slash), and its really likely only to happen between siblings or spouses in my opinion.
