I'll start:
I was highly disappointed by there being a size limit on settlements. Yes, I know consoles aren't powerful enough to just make a large city. Yes, I know that the settlements we can make will likely be larger than any housing we've ever had in a Bethesda game. No, I don't care, I wanted mah city. The idea that no matter what I do, I can't make the largest settlement in the game gets under my skin like crazy.