This blog is updated daily..
A general description is here.
list.files() (also known as dir()) has a new argument
'include.dirs' to control whether directories are included in
the listing: the default of include.dirs = !recursive is
unchanged.
Package 'tools' has new functions checkRdaFiles() and resaveRdaFiles() to report on the format of .rda/.RData data files, and to re-save them in a different compressed format, including choosing the most compact format available.
A new INSTALL option, --resave-data, makes use of this.
New function Sys.readlink() for information about symbolic links, including if a file is a symbolic link.
Printing a list could segfault if the elements are nested too deeply.
cat() on an unopened connection could close it twice, and file() connections segfaulted on some systems..
Help in base and recommended packages is no longer zipped: text, HTML, latex and examples files are now built when needed.
Options --use-zip and --use-zip-help in R CMD INSTALL are no longer available and --auto-zip only zips data (or not).
Help in packages installed under 2.9.x may not work correctly, and a warning is given when such a package is attached by library(). Re-installation of all packages is advised (use update.packages(checkBuilt = TRUE)).
Binary packages are installed without CHM help if they contain it (as those intended for 2.9.x may).
The help default has been changed to be HTML help rather than CHM help. [Not yet the MSI installer.]
Binary packages are installed without CHM help if they contain itfor the standard installer is HTML help rather than CHM help.
The categories in the installers have been simplified. Now the files to support installation of source packages are always installed (they weare now only 0.7Mb), and there are no longer categories 'chtml', 'html/help', 'latex' and 'Rd'.