I put together a Shopping Cart at BH. It doesn't have the 16 in it... I went with the 12 manual focus and the 23, thinking that the 23 is really the superior "Only bringing one lens and it's gonna be dark" lens, which is a scenario I am in pretty frequently. Right now that's being filled by the 35, but it's sometimes too long for interior shots. And the DOF at 1.4 is so thin that I'd gladly trade a little bokeh for more faces in focus at the same operating speed. I can see me ordering the 16, and then wishing I hadn't, because it's TOO wide for a do-it-all dark lens for me, whereas the 23 would really do it all. So then the 12 fills the Extra Wide / Star Shots gap I have, and I'm good.
Side note: the cart also has a cactus off-cam flash setup. It may finally be time...