Wow, this game have awesome Graphic and Music with right SE.
I'm not a fan of stealth game, but I can simple beat them all in this game :P
I use keyboard and can't use slow fall ability ( I read comment below and still can't use this ), so I try roll to skip the spike area, and this attempt success :P
also WASD no any reaction.
I prefer holding down key for crouch, use down key to switch crouch state are pretty difficult to manager.
No comment about stealth game part, but the action part have nice balance.
final boss are quite easy once you figure out the pattern, but I think you can add some use of phase ability before the boss. ( maybe you have planed, just try to point out )