I found the discussion of package version selection in Go interesting:
It places an emphasis on stability and repeatability and rejects opam’s policy to use the latest version. I think it has quite some merits. The way I understand it, it prefers the oldest version compatible with constraints such that newer versions would have to be requested explicitly.
The one downside is that re-buidling does not get the latest patch/bug fix (but I’m not sure). Maybe this could be combined: you get the latest patch within the oldest compatible major/minor version.