It looks like this is much more fine grained compared to mran, i.e., with groundhog, you select the date vs with mran where you use the last (often > year old) snapshot.

mran is a great idea and if Rstudio (the defacto gate-keepers of the faith -- with Hadley the high priest) pushed to use mran, then the R community would follow suit (like they do for everything else).

This would do a lot to bring MS into the fold, which would actually be great for R.