Not too big on modded, but this mod is near perfection. A bit on the powerful side for normal mode, but I will probably use it for expert in the future. However, I found the power-scaling very exciting. It *felt* like metroid, and that should be saying something. Really hope the transition to 1.4 goes well, this mod goes above and beyond to be both mechanically and visually striking.
I think that the extent of player choice is a bit hindered for a Terraria mod, though. I wish the freedom of post-ML were a feature for all of progression. Plenty of morphball bomb iterations to counter this point, although none of them felt especially useful. I think this is where a bit more liberties could be taken. More (perhaps non-canon) alternatives to upgrades like the wave or ice beam could serve to give the hunter class more depth in the way that dart guns or flails give their respective classes more mileage without flat stat increases.
I'm just posting my initial thoughts here, I apologize if these discussions have already been had.
Fantastic mod, 10/10 from me.