The 5.0 Flyknits have an internal seam that chafes my foot and creates a callus on the outer part of my foot.The 4.0 does not have that seam. Because of that, the 4.0 flyknits are much more comfortable for me.
Fit is comfortably snug around the instep. Reasonable amount of arch support (I have to put arch supports in the 5.0's). Lots of room in the toe box. Mesh expands / contracts for a comfortable fit.
Shoes came by the promised date. The shoe box was missing the lid, but the shoes and box bottom were sealed in a plastic bag. The packaging was well done and secure.