Posting this from my Narrative Flow Critique which has gotten buried from all the amazing suggestions :P
-Narrative Flow: I wake up on a beach, a larian staple, and then pick up these potential companions. So far so good, but...I could just make camp with one of them and it leads to a deep conversation...with a person I just met. Very little game time has passed and I'm already talking with this companion about things that should perhaps come later in the story. It makes more sense if I wait to level 2 to head to camp, and have some combat experience, but just hopping into camp right after getting shadowheart felt...awkward. This happened several times throughout the game where I would go into camp and it would lead to some important story bits...but I didn't feel like my character was ready for that bit just yet. Not enough actual time had passed. So, I found myself avoiding going to camp because I didn't want to get pulled into some narrative hook
-Act 1 Ending: It didn't feel like an ending. I didn't feel like I'd accomplished anything of note to define the transition into Act 2. Perhaps this is unrealistic expectations from previous CRPGS, but the end of Act 1 always felt like you'd accomplished something amazing our had developed some real relationships with your teammates. Whereas, going into act 2, I feel like my relationships with my teammates are fairly similar to where they started. Yes, I've learned a bit about them, but nothing momentous has happened. There was no boss fight. No really major accomplishment. Just trudging down the underdark.
-Companions: I really enjoyed the companions...but they're all gary-stus/mary-sue's. Each of them have their own special snow-flakeness to them. Vampire? Check. Explosive wizard? Check. etc. I think there needs to be more cohesion among the writers. As it stands, the companions all feel super-special in their own way, which is nice, but it does two things. One, it makes your custom origin PC seemingly less special and two, it creates a more jilted story. There needs to be more cohesion in the story t elling.
-Origins: I know it would be some work, but I strongly encourage Larian to consider adding 2-3 hours of gameplay around your custom player's origin. For example, you're a Drow-lolth sworn, you spend a few in-game hours learning about your culture and how you got kidnapped by the Mind-flayers. As it stands, I really didn't feel much connection to my PC until about halfway into Act 1. I'd really like to flesh out my pc as a person in game before getting thrown into the insanity.