Spoilers obviously but I really wanted to give it a try but it is such a chore to go through.
Literally nothing incentivizes me to do evil things... well besides doing evil just for being evil. If anything I am penalized for going down that path even though I should probably be incentivized more to be evil rather than good. So if I am good I know that all the tieflings I help will be found in Baldur's Gate so my good actions will have longterm benefit. Apparently if I help Mol I would also have the new thieves' guild as allies? Just so many characters and potential plotlines for Act 2 and 3 that I anticipate in seeing them resolved in the next acts.
There is also the underdark issue where the refugee fungal king wants me to betray my current employer for "rewards"... buddy I am already getting rewards, why should I clear a WHOLE city of friendlies? There are also many unrelated NPCs that will give me quests and show me interesting interactions that I would probably have to kill too. Why? Why should I do that?
It just seems to me the only people that would go down the Evil path are those that are somewhat masochistic and also psychotic. Only the insane would do bad things because it makes them feel good. Larian needs to incentivize me to be evil.
Here are some potential ideas. 1) Give me Sazza as a companion... well more like a subservient underling. I am a True Soul afterall. 2) Give me Minthara as a companion, maybe I can bend her to my allegiance rather than the Absolute's down the road. 3) Give me a Goblin Horn to summon a goblin raiding party to aid me in difficult fights. 4) Give me thralls and minions of true soul. Like the two siblings I meet on the road, they could be interesting characters to learn more about. And who knows maybe to torment or reward as I see fit. 5) Give me the option of not killing the refugees and druids in a massive massacre. Weren't there talk of slave traders in Goblin Fortress? Give me choices! Maybe certain characters can be spared and sold, Why should I kill Mol and her buddies when I can just spare them and have them work for me!
There are a lot of options. Maybe the evil playthrough can impact my camp look as well. It would become more savage looking, maybe I can hire Drow and Ogre merceneries. Have evil pillage and conquest questlines... something! Honestly burning the orphanage just because it makes me so edgy is not that attractive of a choice.
Anyway that's my 2cents. I did not find the evil play through interesting at all.