As a minor update to the R 3.3 series, this update focuses mainly on fixing bugs and doesn't make any major changes to the langauge. As a result, you can expect existing scripts and packages to continue to work if you're upgrading from R 3.3.1. This update includes some performance improvements (particularly in calculation of eigenvalues), better handling of date axes in graphics, and improved documentation for the methods package. (Fun fact: when printed as a 9Mb PDF reference manual, the documentation for the R base and recommended packages now runs to 3452 pages. That's almost 3 copies of War and Peace!)
The nickname for this release is “Sincere Pumpkin Patch”, in recognition of the Halowe'en release date and (per RWeekly) references this clip from “It's the Great Pumpkin, Charlie Brown”.
For the official announcement from the R core team including the detailed list of changes, see the posting in the R-announce mailing list linked below.
R-announce mailing list: R 3.3.2 is released