Andrew Gelman recently lamented the lack of an easy upgrade process for R (probably more relevant on Windows that Linux). Does anyone have a good trick for doing the upgrade, from installing the software to copying all the settings/packages over?

This suggestion was contained in the comments and is what I've been using recently. First you install the new version, then run this in the old verion:

#--run in the old version of R
setwd("C:/Temp/")
packages <- installed.packages()[,"Package"]
save(packages, file="Rpackages")

Followed by this in the new version:

#--run in the new version
setwd("C:/Temp/")
load("Rpackages")
for (p in setdiff(packages, installed.packages()[,"Package"]))
install.packages(p)