As someone who played Dark Urge up to chapter 3, but didn’t finish it, here are my thoughts. Spoiler warning!!!:

-Establishing your character as having issues in ACT 1 is a good thing, as you do something horrible without any skill check or saving throw.
-Being able to fall into temptation is good and all, but it runs into a problem of hindering you without offering any incentive. You can commit some brutal acts 1 in ACT 1, like biting off a goblin's toe, tearing birds wings off, etc.

However, this falls into a problem of the whole game. Being Evil is simply worse and not worth it. You don't get extra stuff, extra content, alternate quests, etc. The urge only gives you stuff, if you commit very specific acts. To make matters worse, you often Miss out on approval and are better off doing skill checks.

One way to fix this is by having something like a tadpole mechanic, we never got in the first place. The more you commit to urge, the better the rewards, but at a price. Companion disapproval is one way to do that (all, but maybe Minthara and Laezel should lose approval).

-There is a very good cutscene in ACT 2 if you resist the urge and I loved every part of it. But, it's just one cutscene. And with ACT 3 being as unfinished as it is, I don’t feel like going through the rest of it, just to get a chance to see something.

-Adding a saving throw to every conversations, where you resist your Dark Urge would get annoying very soon.

So, basically evil should be tempting, but it is not, you just play as a murderhobo and Miss out on stuff for a lacklustre rewards.

Also the reward for commiting to the Urge is Terrible!

The Slayer Form
is just pure garbage!

It has got no resistances, no damage immunities
no condition immunities and mediocore damage against targets that can’t bleed. It also suffers from similar issues as a Wildshape does.

I wrote a whole post about it, but cant find it as of right now.